diff --git a/.claude/settings.local.json b/.claude/settings.local.json
new file mode 100644
index 00000000..cb8a1f05
--- /dev/null
+++ b/.claude/settings.local.json
@@ -0,0 +1,7 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(cargo test:*)"
+    ]
+  }
+}
diff --git a/benchmarks/btreemap/canbench_results.yml b/benchmarks/btreemap/canbench_results.yml
index 2dabed3e..55fef468 100644
--- a/benchmarks/btreemap/canbench_results.yml
+++ b/benchmarks/btreemap/canbench_results.yml
@@ -601,304 +601,325 @@ benches:
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
+  btreemap_v2_heap_memory_used_blob_1024_128:
+    total:
+      calls: 1
+      instructions: 207
+      heap_increase: 0
+      stable_memory_increase: 0
+    scopes: {}
+  btreemap_v2_heap_memory_used_blob_4_128:
+    total:
+      calls: 1
+      instructions: 207
+      heap_increase: 0
+      stable_memory_increase: 0
+    scopes: {}
+  btreemap_v2_heap_memory_used_vec_32_128:
+    total:
+      calls: 1
+      instructions: 207
+      heap_increase: 0
+      stable_memory_increase: 0
+    scopes: {}
   btreemap_v2_insert_10mib_values:
     total:
       calls: 1
-      instructions: 4388592719
+      instructions: 4387226354
       heap_increase: 161
       stable_memory_increase: 3613
     scopes: {}
   btreemap_v2_insert_blob8_u64:
     total:
       calls: 1
-      instructions: 436633391
+      instructions: 436629416
       heap_increase: 0
       stable_memory_increase: 4
     scopes: {}
   btreemap_v2_insert_blob_1024_128:
     total:
       calls: 1
-      instructions: 5496222167
+      instructions: 5496218165
       heap_increase: 0
       stable_memory_increase: 196
     scopes: {}
   btreemap_v2_insert_blob_128_128:
     total:
       calls: 1
-      instructions: 1180838234
+      instructions: 1180834208
       heap_increase: 0
       stable_memory_increase: 46
     scopes: {}
   btreemap_v2_insert_blob_16_128:
     total:
       calls: 1
-      instructions: 486249812
+      instructions: 486246194
       heap_increase: 0
       stable_memory_increase: 24
     scopes: {}
   btreemap_v2_insert_blob_256_128:
     total:
       calls: 1
-      instructions: 1789038066
+      instructions: 1789034049
       heap_increase: 0
       stable_memory_increase: 67
     scopes: {}
   btreemap_v2_insert_blob_32_0:
     total:
       calls: 1
-      instructions: 490459106
+      instructions: 490455134
       heap_increase: 0
       stable_memory_increase: 8
     scopes: {}
   btreemap_v2_insert_blob_32_1024:
     total:
       calls: 1
-      instructions: 703500065
+      instructions: 703496225
       heap_increase: 0
       stable_memory_increase: 173
     scopes: {}
   btreemap_v2_insert_blob_32_128:
     total:
       calls: 1
-      instructions: 542568143
+      instructions: 542564351
       heap_increase: 0
       stable_memory_increase: 28
     scopes: {}
   btreemap_v2_insert_blob_32_16:
     total:
       calls: 1
-      instructions: 519117156
+      instructions: 519113244
       heap_increase: 0
       stable_memory_increase: 11
     scopes: {}
   btreemap_v2_insert_blob_32_256:
     total:
       calls: 1
-      instructions: 570690137
+      instructions: 570686267
       heap_increase: 0
       stable_memory_increase: 49
     scopes: {}
   btreemap_v2_insert_blob_32_32:
     total:
       calls: 1
-      instructions: 528951192
+      instructions: 528947313
       heap_increase: 0
       stable_memory_increase: 13
     scopes: {}
   btreemap_v2_insert_blob_32_4:
     total:
       calls: 1
-      instructions: 509380036
+      instructions: 509376109
       heap_increase: 0
       stable_memory_increase: 8
     scopes: {}
   btreemap_v2_insert_blob_32_512:
     total:
       calls: 1
-      instructions: 610063051
+      instructions: 610059178
       heap_increase: 0
       stable_memory_increase: 91
     scopes: {}
   btreemap_v2_insert_blob_32_64:
     total:
       calls: 1
-      instructions: 534921249
+      instructions: 534917409
       heap_increase: 0
       stable_memory_increase: 18
     scopes: {}
   btreemap_v2_insert_blob_32_8:
     total:
       calls: 1
-      instructions: 517593840
+      instructions: 517590057
       heap_increase: 0
       stable_memory_increase: 9
     scopes: {}
   btreemap_v2_insert_blob_4_128:
     total:
       calls: 1
-      instructions: 407268940
+      instructions: 407266843
       heap_increase: 0
       stable_memory_increase: 13
     scopes: {}
   btreemap_v2_insert_blob_512_128:
     total:
       calls: 1
-      instructions: 3041223382
+      instructions: 3041219347
       heap_increase: 0
       stable_memory_increase: 111
     scopes: {}
   btreemap_v2_insert_blob_64_128:
     total:
       calls: 1
-      instructions: 661179485
+      instructions: 661175552
       heap_increase: 0
       stable_memory_increase: 34
     scopes: {}
   btreemap_v2_insert_blob_8_128:
     total:
       calls: 1
-      instructions: 458615568
+      instructions: 458612442
       heap_increase: 0
       stable_memory_increase: 20
     scopes: {}
   btreemap_v2_insert_principal:
     total:
       calls: 1
-      instructions: 503308324
+      instructions: 503303086
       heap_increase: 0
       stable_memory_increase: 8
     scopes: {}
   btreemap_v2_insert_u64_blob8:
     total:
       calls: 1
-      instructions: 406744693
+      instructions: 406739905
       heap_increase: 0
       stable_memory_increase: 5
     scopes: {}
   btreemap_v2_insert_u64_u64:
     total:
       calls: 1
-      instructions: 414580548
+      instructions: 414575469
       heap_increase: 0
       stable_memory_increase: 6
     scopes: {}
   btreemap_v2_insert_u64_vec8:
     total:
       calls: 1
-      instructions: 410372254
+      instructions: 410368222
       heap_increase: 0
       stable_memory_increase: 21
     scopes: {}
   btreemap_v2_insert_vec8_u64:
     total:
       calls: 1
-      instructions: 594103663
+      instructions: 594100537
       heap_increase: 0
       stable_memory_increase: 16
     scopes: {}
   btreemap_v2_insert_vec_1024_128:
     total:
       calls: 1
-      instructions: 2744606200
+      instructions: 2744513878
       heap_increase: 0
       stable_memory_increase: 193
     scopes: {}
   btreemap_v2_insert_vec_128_128:
     total:
       calls: 1
-      instructions: 1012643373
+      instructions: 1012625574
       heap_increase: 0
       stable_memory_increase: 51
     scopes: {}
   btreemap_v2_insert_vec_16_128:
     total:
       calls: 1
-      instructions: 708997439
+      instructions: 708984362
       heap_increase: 0
       stable_memory_increase: 31
     scopes: {}
   btreemap_v2_insert_vec_256_128:
     total:
       calls: 1
-      instructions: 1402219761
+      instructions: 1402182234
       heap_increase: 0
       stable_memory_increase: 71
     scopes: {}
   btreemap_v2_insert_vec_32_0:
     total:
       calls: 1
-      instructions: 621849784
+      instructions: 621845953
       heap_increase: 0
       stable_memory_increase: 20
     scopes: {}
   btreemap_v2_insert_vec_32_1024:
     total:
       calls: 1
-      instructions: 1182132701
+      instructions: 1182054323
       heap_increase: 0
       stable_memory_increase: 171
     scopes: {}
   btreemap_v2_insert_vec_32_128:
     total:
       calls: 1
-      instructions: 756106158
+      instructions: 756092289
       heap_increase: 0
       stable_memory_increase: 33
     scopes: {}
   btreemap_v2_insert_vec_32_16:
     total:
       calls: 1
-      instructions: 666191903
+      instructions: 666188006
       heap_increase: 0
       stable_memory_increase: 20
     scopes: {}
   btreemap_v2_insert_vec_32_256:
     total:
       calls: 1
-      instructions: 869225881
+      instructions: 869200138
       heap_increase: 0
       stable_memory_increase: 54
     scopes: {}
   btreemap_v2_insert_vec_32_32:
     total:
       calls: 1
-      instructions: 661645394
+      instructions: 661641515
       heap_increase: 0
       stable_memory_increase: 20
     scopes: {}
   btreemap_v2_insert_vec_32_4:
     total:
       calls: 1
-      instructions: 660354036
+      instructions: 660350181
       heap_increase: 0
       stable_memory_increase: 20
     scopes: {}
   btreemap_v2_insert_vec_32_512:
     total:
       calls: 1
-      instructions: 973664463
+      instructions: 973623252
       heap_increase: 0
       stable_memory_increase: 91
     scopes: {}
   btreemap_v2_insert_vec_32_64:
     total:
       calls: 1
-      instructions: 691643081
+      instructions: 691630844
       heap_increase: 0
       stable_memory_increase: 24
     scopes: {}
   btreemap_v2_insert_vec_32_8:
     total:
       calls: 1
-      instructions: 659845953
+      instructions: 659842170
       heap_increase: 0
       stable_memory_increase: 20
     scopes: {}
   btreemap_v2_insert_vec_4_128:
     total:
       calls: 1
-      instructions: 604355928
+      instructions: 604348722
       heap_increase: 0
       stable_memory_increase: 16
     scopes: {}
   btreemap_v2_insert_vec_512_128:
     total:
       calls: 1
-      instructions: 1859161681
+      instructions: 1859108239
       heap_increase: 0
       stable_memory_increase: 112
     scopes: {}
   btreemap_v2_insert_vec_64_128:
     total:
       calls: 1
-      instructions: 846320282
+      instructions: 846297779
       heap_increase: 0
       stable_memory_increase: 41
     scopes: {}
   btreemap_v2_insert_vec_8_128:
     total:
       calls: 1
-      instructions: 666289233
+      instructions: 666278550
       heap_increase: 0
       stable_memory_increase: 23
     scopes: {}
@@ -975,658 +996,658 @@ benches:
   btreemap_v2_mem_manager_insert_blob512_u64:
     total:
       calls: 1
-      instructions: 3127680452
+      instructions: 3127693876
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_mem_manager_insert_u64_blob512:
     total:
       calls: 1
-      instructions: 607288370
+      instructions: 607302030
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_mem_manager_insert_u64_u64:
     total:
       calls: 1
-      instructions: 520545864
+      instructions: 520562305
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_mem_manager_insert_u64_vec512:
     total:
       calls: 1
-      instructions: 834100595
+      instructions: 834230066
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_mem_manager_insert_vec512_u64:
     total:
       calls: 1
-      instructions: 1964405448
+      instructions: 1964533302
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_mem_manager_remove_blob512_u64:
     total:
       calls: 1
-      instructions: 4310221225
+      instructions: 4310230683
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_mem_manager_remove_u64_blob512:
     total:
       calls: 1
-      instructions: 882970074
+      instructions: 882979670
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_mem_manager_remove_u64_u64:
     total:
       calls: 1
-      instructions: 736785650
+      instructions: 736797990
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_mem_manager_remove_u64_vec512:
     total:
       calls: 1
-      instructions: 1223804753
+      instructions: 1223992077
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_mem_manager_remove_vec512_u64:
     total:
       calls: 1
-      instructions: 3084565257
+      instructions: 3084753399
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob8_u64:
     total:
       calls: 1
-      instructions: 599256189
+      instructions: 599252070
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_1024_128:
     total:
       calls: 1
-      instructions: 8387602842
+      instructions: 8387598840
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_128_128:
     total:
       calls: 1
-      instructions: 1824725965
+      instructions: 1824721939
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_16_128:
     total:
       calls: 1
-      instructions: 743084112
+      instructions: 743080488
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_256_128:
     total:
       calls: 1
-      instructions: 2763911828
+      instructions: 2763907811
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_32_0:
     total:
       calls: 1
-      instructions: 751497584
+      instructions: 751493486
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_32_1024:
     total:
       calls: 1
-      instructions: 1121481321
+      instructions: 1121477481
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_32_128:
     total:
       calls: 1
-      instructions: 860285162
+      instructions: 860281370
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_32_16:
     total:
       calls: 1
-      instructions: 795095715
+      instructions: 795091803
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_32_256:
     total:
       calls: 1
-      instructions: 891739804
+      instructions: 891735934
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_32_32:
     total:
       calls: 1
-      instructions: 808560505
+      instructions: 808556626
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_32_4:
     total:
       calls: 1
-      instructions: 778864648
+      instructions: 778860667
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_32_512:
     total:
       calls: 1
-      instructions: 957571175
+      instructions: 957567308
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_32_64:
     total:
       calls: 1
-      instructions: 817406508
+      instructions: 817402668
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_32_8:
     total:
       calls: 1
-      instructions: 796779002
+      instructions: 796775177
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_4_128:
     total:
       calls: 1
-      instructions: 371435725
+      instructions: 371433628
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_512_128:
     total:
       calls: 1
-      instructions: 4613700344
+      instructions: 4613696303
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_64_128:
     total:
       calls: 1
-      instructions: 1031695256
+      instructions: 1031691323
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_blob_8_128:
     total:
       calls: 1
-      instructions: 604976184
+      instructions: 604973040
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_principal:
     total:
       calls: 1
-      instructions: 800191973
+      instructions: 800186729
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_u64_blob8:
     total:
       calls: 1
-      instructions: 669276877
+      instructions: 669272017
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_u64_u64:
     total:
       calls: 1
-      instructions: 681264462
+      instructions: 681259383
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_u64_vec8:
     total:
       calls: 1
-      instructions: 671829217
+      instructions: 671825185
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec8_u64:
     total:
       calls: 1
-      instructions: 782876135
+      instructions: 782873009
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_1024_128:
     total:
       calls: 1
-      instructions: 4049265076
+      instructions: 4049152840
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_128_128:
     total:
       calls: 1
-      instructions: 1503218744
+      instructions: 1503200945
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_16_128:
     total:
       calls: 1
-      instructions: 1024772148
+      instructions: 1024759071
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_256_128:
     total:
       calls: 1
-      instructions: 2019891066
+      instructions: 2019833997
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_32_0:
     total:
       calls: 1
-      instructions: 862946599
+      instructions: 862942768
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_32_1024:
     total:
       calls: 1
-      instructions: 1689829372
+      instructions: 1689732148
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_32_128:
     total:
       calls: 1
-      instructions: 1088869698
+      instructions: 1088853861
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_32_16:
     total:
       calls: 1
-      instructions: 928270806
+      instructions: 928266909
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_32_256:
     total:
       calls: 1
-      instructions: 1215466767
+      instructions: 1215441024
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_32_32:
     total:
       calls: 1
-      instructions: 931028208
+      instructions: 931024329
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_32_4:
     total:
       calls: 1
-      instructions: 914745699
+      instructions: 914741844
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_32_512:
     total:
       calls: 1
-      instructions: 1373268399
+      instructions: 1373208474
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_32_64:
     total:
       calls: 1
-      instructions: 972735601
+      instructions: 972723364
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_32_8:
     total:
       calls: 1
-      instructions: 924967663
+      instructions: 924963880
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_4_128:
     total:
       calls: 1
-      instructions: 540984708
+      instructions: 540977502
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_512_128:
     total:
       calls: 1
-      instructions: 2716330411
+      instructions: 2716276969
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_64_128:
     total:
       calls: 1
-      instructions: 1234556907
+      instructions: 1234517190
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_first_vec_8_128:
     total:
       calls: 1
-      instructions: 850734232
+      instructions: 850723549
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob8_u64:
     total:
       calls: 1
-      instructions: 575661530
+      instructions: 575657399
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_1024_128:
     total:
       calls: 1
-      instructions: 8055247791
+      instructions: 8055243789
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_128_128:
     total:
       calls: 1
-      instructions: 1755509118
+      instructions: 1755505092
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_16_128:
     total:
       calls: 1
-      instructions: 716556083
+      instructions: 716552465
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_256_128:
     total:
       calls: 1
-      instructions: 2669730307
+      instructions: 2669726290
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_32_0:
     total:
       calls: 1
-      instructions: 723335313
+      instructions: 723331257
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_32_1024:
     total:
       calls: 1
-      instructions: 1085450731
+      instructions: 1085446885
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_32_128:
     total:
       calls: 1
-      instructions: 825902306
+      instructions: 825898514
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_32_16:
     total:
       calls: 1
-      instructions: 766901397
+      instructions: 766897485
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_32_256:
     total:
       calls: 1
-      instructions: 860879651
+      instructions: 860875781
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_32_32:
     total:
       calls: 1
-      instructions: 775936416
+      instructions: 775932537
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_32_4:
     total:
       calls: 1
-      instructions: 755124599
+      instructions: 755120630
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_32_512:
     total:
       calls: 1
-      instructions: 932320719
+      instructions: 932316858
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_32_64:
     total:
       calls: 1
-      instructions: 791545690
+      instructions: 791541850
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_32_8:
     total:
       calls: 1
-      instructions: 768161716
+      instructions: 768157909
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_4_128:
     total:
       calls: 1
-      instructions: 357885021
+      instructions: 357882924
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_512_128:
     total:
       calls: 1
-      instructions: 4444567386
+      instructions: 4444563339
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_64_128:
     total:
       calls: 1
-      instructions: 999738711
+      instructions: 999734778
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_blob_8_128:
     total:
       calls: 1
-      instructions: 598942864
+      instructions: 598939732
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_principal:
     total:
       calls: 1
-      instructions: 780291969
+      instructions: 780286737
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_u64_blob8:
     total:
       calls: 1
-      instructions: 645812582
+      instructions: 645807686
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_u64_u64:
     total:
       calls: 1
-      instructions: 657455588
+      instructions: 657450509
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_u64_vec8:
     total:
       calls: 1
-      instructions: 648268033
+      instructions: 648264001
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec8_u64:
     total:
       calls: 1
-      instructions: 759547094
+      instructions: 759543968
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_1024_128:
     total:
       calls: 1
-      instructions: 4254818123
+      instructions: 4254705881
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_128_128:
     total:
       calls: 1
-      instructions: 1509650210
+      instructions: 1509632411
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_16_128:
     total:
       calls: 1
-      instructions: 1006125814
+      instructions: 1006112737
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_256_128:
     total:
       calls: 1
-      instructions: 2073363853
+      instructions: 2073306796
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_32_0:
     total:
       calls: 1
-      instructions: 846109662
+      instructions: 846105831
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_32_1024:
     total:
       calls: 1
-      instructions: 1664437667
+      instructions: 1664340419
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_32_128:
     total:
       calls: 1
-      instructions: 1064611264
+      instructions: 1064595433
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_32_16:
     total:
       calls: 1
-      instructions: 902974455
+      instructions: 902970558
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_32_256:
     total:
       calls: 1
-      instructions: 1193452039
+      instructions: 1193426296
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_32_32:
     total:
       calls: 1
-      instructions: 910490347
+      instructions: 910486468
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_32_4:
     total:
       calls: 1
-      instructions: 898985596
+      instructions: 898981741
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_32_512:
     total:
       calls: 1
-      instructions: 1356914135
+      instructions: 1356854198
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_32_64:
     total:
       calls: 1
-      instructions: 949782755
+      instructions: 949770518
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_32_8:
     total:
       calls: 1
-      instructions: 902473492
+      instructions: 902469709
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_4_128:
     total:
       calls: 1
-      instructions: 527064939
+      instructions: 527057733
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_512_128:
     total:
       calls: 1
-      instructions: 2808165041
+      instructions: 2808111599
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_64_128:
     total:
       calls: 1
-      instructions: 1220824533
+      instructions: 1220784792
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_pop_last_vec_8_128:
     total:
       calls: 1
-      instructions: 850619579
+      instructions: 850608896
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
@@ -1696,301 +1717,301 @@ benches:
   btreemap_v2_remove_10mib_values:
     total:
       calls: 1
-      instructions: 4711118385
+      instructions: 4709565702
       heap_increase: 0
       stable_memory_increase: 657
     scopes: {}
   btreemap_v2_remove_blob8_u64:
     total:
       calls: 1
-      instructions: 584636969
+      instructions: 584632796
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_1024_128:
     total:
       calls: 1
-      instructions: 7363800309
+      instructions: 7363796307
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_128_128:
     total:
       calls: 1
-      instructions: 1588756329
+      instructions: 1588752303
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_16_128:
     total:
       calls: 1
-      instructions: 665337905
+      instructions: 665334293
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_256_128:
     total:
       calls: 1
-      instructions: 2421697300
+      instructions: 2421693283
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_32_0:
     total:
       calls: 1
-      instructions: 654250005
+      instructions: 654246003
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_32_1024:
     total:
       calls: 1
-      instructions: 985325869
+      instructions: 985322023
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_32_128:
     total:
       calls: 1
-      instructions: 746608890
+      instructions: 746605092
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_32_16:
     total:
       calls: 1
-      instructions: 700059994
+      instructions: 700056094
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_32_256:
     total:
       calls: 1
-      instructions: 784125701
+      instructions: 784121825
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_32_32:
     total:
       calls: 1
-      instructions: 711919498
+      instructions: 711915619
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_32_4:
     total:
       calls: 1
-      instructions: 696214241
+      instructions: 696210302
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_32_512:
     total:
       calls: 1
-      instructions: 857936684
+      instructions: 857932817
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_32_64:
     total:
       calls: 1
-      instructions: 737074307
+      instructions: 737070467
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_32_8:
     total:
       calls: 1
-      instructions: 696057915
+      instructions: 696054096
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_4_128:
     total:
       calls: 1
-      instructions: 452857933
+      instructions: 452855812
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_512_128:
     total:
       calls: 1
-      instructions: 4071507249
+      instructions: 4071503214
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_64_128:
     total:
       calls: 1
-      instructions: 910052271
+      instructions: 910048338
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_blob_8_128:
     total:
       calls: 1
-      instructions: 599299651
+      instructions: 599296531
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_principal:
     total:
       calls: 1
-      instructions: 684159422
+      instructions: 684154256
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_u64_blob8:
     total:
       calls: 1
-      instructions: 566079913
+      instructions: 566075041
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_u64_u64:
     total:
       calls: 1
-      instructions: 586718731
+      instructions: 586713652
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_u64_vec8:
     total:
       calls: 1
-      instructions: 571366355
+      instructions: 571362323
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec8_u64:
     total:
       calls: 1
-      instructions: 755823918
+      instructions: 755820792
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_1024_128:
     total:
       calls: 1
-      instructions: 4475943466
+      instructions: 4475823940
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_128_128:
     total:
       calls: 1
-      instructions: 1418213214
+      instructions: 1418195415
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_16_128:
     total:
       calls: 1
-      instructions: 921111290
+      instructions: 921098213
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_256_128:
     total:
       calls: 1
-      instructions: 2244668594
+      instructions: 2244605357
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_32_0:
     total:
       calls: 1
-      instructions: 834330028
+      instructions: 834326197
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_32_1024:
     total:
       calls: 1
-      instructions: 1701563272
+      instructions: 1701459670
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_32_128:
     total:
       calls: 1
-      instructions: 1036968514
+      instructions: 1036942087
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_32_16:
     total:
       calls: 1
-      instructions: 871328883
+      instructions: 871324986
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_32_256:
     total:
       calls: 1
-      instructions: 1240176546
+      instructions: 1240150803
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_32_32:
     total:
       calls: 1
-      instructions: 867569469
+      instructions: 867565590
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_32_4:
     total:
       calls: 1
-      instructions: 862147420
+      instructions: 862143565
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_32_512:
     total:
       calls: 1
-      instructions: 1405971132
+      instructions: 1405903551
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_32_64:
     total:
       calls: 1
-      instructions: 968312981
+      instructions: 968300744
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_32_8:
     total:
       calls: 1
-      instructions: 856477157
+      instructions: 856473374
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_4_128:
     total:
       calls: 1
-      instructions: 662121914
+      instructions: 662114708
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_512_128:
     total:
       calls: 1
-      instructions: 3082706271
+      instructions: 3082652829
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_64_128:
     total:
       calls: 1
-      instructions: 1183958569
+      instructions: 1183921648
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
   btreemap_v2_remove_vec_8_128:
     total:
       calls: 1
-      instructions: 821774415
+      instructions: 821763732
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
@@ -2120,4 +2141,46 @@ benches:
       heap_increase: 0
       stable_memory_increase: 0
     scopes: {}
+  btreemap_v2_stable_memory_size_blob_1024_128:
+    total:
+      calls: 1
+      instructions: 207
+      heap_increase: 0
+      stable_memory_increase: 0
+    scopes: {}
+  btreemap_v2_stable_memory_size_blob_4_128:
+    total:
+      calls: 1
+      instructions: 207
+      heap_increase: 0
+      stable_memory_increase: 0
+    scopes: {}
+  btreemap_v2_stable_memory_size_vec_32_128:
+    total:
+      calls: 1
+      instructions: 207
+      heap_increase: 0
+      stable_memory_increase: 0
+    scopes: {}
+  btreemap_v2_stable_memory_used_blob_1024_128:
+    total:
+      calls: 1
+      instructions: 207
+      heap_increase: 0
+      stable_memory_increase: 0
+    scopes: {}
+  btreemap_v2_stable_memory_used_blob_4_128:
+    total:
+      calls: 1
+      instructions: 207
+      heap_increase: 0
+      stable_memory_increase: 0
+    scopes: {}
+  btreemap_v2_stable_memory_used_vec_32_128:
+    total:
+      calls: 1
+      instructions: 207
+      heap_increase: 0
+      stable_memory_increase: 0
+    scopes: {}
 version: 0.2.0
diff --git a/benchmarks/btreemap/src/main.rs b/benchmarks/btreemap/src/main.rs
index 167b973c..945f6747 100644
--- a/benchmarks/btreemap/src/main.rs
+++ b/benchmarks/btreemap/src/main.rs
@@ -815,4 +815,52 @@ fn range_count_helper_v2(count: usize, size: usize) -> BenchResult {
     })
 }
 
+// Benchmarks for memory reporting methods.
+
+fn populate_btree_v2<K: TestKey, V: TestValue>() -> BTreeMap<K, V, DefaultMemoryImpl> {
+    let mut btree = BTreeMap::new(DefaultMemoryImpl::default());
+    let mut rng = Rng::from_seed(0);
+    let items = generate_random_kv::<K, V>(10_000, &mut rng);
+    for (k, v) in items {
+        btree.insert(k, v);
+    }
+    btree
+}
+
+fn heap_memory_used_helper<K: TestKey, V: TestValue>() -> BenchResult {
+    let btree = populate_btree_v2::<K, V>();
+    bench_fn(|| {
+        let _ = btree.heap_memory_used();
+    })
+}
+
+fn stable_memory_size_helper<K: TestKey, V: TestValue>() -> BenchResult {
+    let btree = populate_btree_v2::<K, V>();
+    bench_fn(|| {
+        let _ = btree.stable_memory_size();
+    })
+}
+
+fn stable_memory_used_helper<K: TestKey, V: TestValue>() -> BenchResult {
+    let btree = populate_btree_v2::<K, V>();
+    bench_fn(|| {
+        let _ = btree.stable_memory_used();
+    })
+}
+
+bench_tests! {
+    // Small bounded, large bounded, unbounded.
+    btreemap_v2_heap_memory_used_blob_4_128,    heap_memory_used_helper,          Blob4, Blob128;
+    btreemap_v2_heap_memory_used_blob_1024_128, heap_memory_used_helper,       Blob1024, Blob128;
+    btreemap_v2_heap_memory_used_vec_32_128,    heap_memory_used_helper,  UnboundedVecN32, UnboundedVecN128;
+
+    btreemap_v2_stable_memory_size_blob_4_128,    stable_memory_size_helper,          Blob4, Blob128;
+    btreemap_v2_stable_memory_size_blob_1024_128, stable_memory_size_helper,       Blob1024, Blob128;
+    btreemap_v2_stable_memory_size_vec_32_128,    stable_memory_size_helper,  UnboundedVecN32, UnboundedVecN128;
+
+    btreemap_v2_stable_memory_used_blob_4_128,    stable_memory_used_helper,          Blob4, Blob128;
+    btreemap_v2_stable_memory_used_blob_1024_128, stable_memory_used_helper,       Blob1024, Blob128;
+    btreemap_v2_stable_memory_used_vec_32_128,    stable_memory_used_helper,  UnboundedVecN32, UnboundedVecN128;
+}
+
 fn main() {}
diff --git a/src/btreemap.rs b/src/btreemap.rs
index c6f4ae92..fc4503fa 100644
--- a/src/btreemap.rs
+++ b/src/btreemap.rs
@@ -53,9 +53,10 @@ mod iter;
 mod node;
 use crate::btreemap::iter::{IterInternal, KeysIter, ValuesIter};
 use crate::{
+    mem_size::MemSize,
     storable::Bound as StorableBound,
     types::{Address, NULL},
-    Memory, Storable,
+    Memory, Storable, WASM_PAGE_SIZE,
 };
 use allocator::Allocator;
 pub use iter::Iter;
@@ -252,6 +253,22 @@ where
     _phantom: PhantomData<(K, V)>,
 }
 
+impl<K, V, M> MemSize for BTreeMap<K, V, M>
+where
+    K: Storable + Ord + Clone,
+    V: Storable,
+    M: Memory,
+{
+    fn mem_size(&self) -> usize {
+        // Excludes _phantom (zero-size) and the Memory handle
+        // (reported separately via stable_memory_size).
+        self.root_addr.mem_size()
+            + self.version.mem_size()
+            + self.allocator.mem_size()
+            + self.length.mem_size()
+    }
+}
+
 #[derive(PartialEq, Debug)]
 /// The packed header size must be <= ALLOCATOR_OFFSET.
 struct BTreeHeader {
@@ -392,6 +409,60 @@ where
         btree
     }
 
+    /// Returns the amount of heap and stack memory used in bytes.
+    pub fn heap_memory_used(&self) -> usize {
+        self.mem_size()
+    }
+
+    /// Returns the amount of stable memory allocated in bytes.
+    pub fn stable_memory_size(&self) -> usize {
+        (self.allocator.memory().size() * WASM_PAGE_SIZE) as usize
+    }
+
+    /// Returns the exact height of the tree by walking from root to a leaf.
+    ///
+    /// Returns 0 for an empty tree. Requires O(height) stable memory reads,
+    /// which is typically 3–5 for millions of entries.
+    #[cfg(test)]
+    fn height(&self) -> u32 {
+        if self.root_addr == NULL {
+            return 0;
+        }
+        let mut height = 1;
+        let mut node = self.load_node(self.root_addr);
+        while node.node_type() == NodeType::Internal {
+            node = self.load_node(node.child(0));
+            height += 1;
+        }
+        height
+    }
+
+    /// Estimates the tree height from the number of entries. O(1).
+    ///
+    /// Uses `ceil(log_B(n))` with an occupancy correction factor.
+    /// May differ from the actual height by ±1 in some cases.
+    pub fn height_approx(&self) -> u32 {
+        let n = self.length;
+        if n == 0 {
+            return 0;
+        }
+        // Average node occupancy after random inserts is ~69% (ln 2).
+        // Use B * 1.3 ≈ effective fan-out (conservative: slightly under ln 2).
+        let effective_b = (node::B as f64) * 1.3;
+        // max(1, ...) because a non-empty tree always has at least height 1.
+        std::cmp::max(1, (n as f64).log(effective_b).ceil() as u32)
+    }
+
+    /// Returns the approximate amount of stable memory actually used in bytes.
+    pub fn stable_memory_used(&self) -> usize {
+        // BTreeMap header + allocator header + allocated chunks.
+        // O(1): uses the cached chunk count, no node traversal.
+        (ALLOCATOR_OFFSET as u64
+            + Allocator::<M>::header_size().get()
+            + self.allocator.num_allocated_chunks() * self.allocator.chunk_size().get())
+            as usize
+    }
+
     /// Loads the map from memory.
     pub fn load(memory: M) -> Self {
         Self::load_helper(memory, true)
@@ -3378,4 +3449,161 @@ mod test {
 
         assert_eq!(btree.allocator.num_allocated_chunks(), 0);
     }
+
+    #[test]
+    fn memory_reporting_empty() {
+        let mem = make_memory();
+        let btree = BTreeMap::<u32, u32, _>::new(mem);
+
+        // BTreeMap holds Address(8) + Version(16) + Allocator fields(20) + u64(8) = 52 bytes.
+        // No heap allocations, so heap_memory_used == sum of inline field sizes.
+        // Update this value if the struct layout changes.
+        assert_eq!(btree.heap_memory_used(), 52);
+
+        // One WASM page (64 KiB) is allocated on init.
+        assert_eq!(btree.stable_memory_size(), WASM_PAGE_SIZE as usize);
+
+        // Only the BTreeMap header (52 bytes) + AllocatorHeader (48 bytes) = 100 bytes used.
+        let base_used = ALLOCATOR_OFFSET + Allocator::<VectorMemory>::header_size().get() as usize;
+        assert_eq!(base_used, 100);
+        assert_eq!(btree.stable_memory_used(), base_used);
+    }
+
+    #[test]
+    fn memory_reporting_insert_and_remove() {
+        let mem = make_memory();
+        let mut btree = BTreeMap::<u32, u32, _>::new(mem);
+
+        let base_used = btree.stable_memory_used();
+        let chunk_size = btree.allocator.chunk_size().get() as usize;
+
+        for i in 0..100u32 {
+            btree.insert(i, i);
+        }
+
+        // 100 entries in a V2 BTreeMap<u32, u32> produce 19 nodes (chunks).
+        let chunks = btree.allocator.num_allocated_chunks();
+        assert_eq!(chunks, 19);
+        assert_eq!(
+            btree.stable_memory_used(),
+            base_used + chunks as usize * chunk_size
+        );
+        assert!(btree.stable_memory_used() <= btree.stable_memory_size());
+
+        // After removing all entries, used drops back to base (0 allocated chunks).
+        for i in 0..100u32 {
+            btree.remove(&i);
+        }
+        assert_eq!(btree.allocator.num_allocated_chunks(), 0);
+        assert_eq!(btree.stable_memory_used(), base_used);
+
+        // Stable memory size never shrinks — still one page.
+        assert_eq!(btree.stable_memory_size(), WASM_PAGE_SIZE as usize);
+    }
+
+    /// Verifies memory reporting invariants for a given K/V combination:
+    /// - heap_memory_used is consistent across types (same struct layout)
+    /// - stable_memory_used grows after inserts and returns to base after removal
+    /// - stable_memory_used <= stable_memory_size always
+    fn memory_reporting_for_type<K: TestKey, V: TestValue>() {
+        let mem = make_memory();
+        let mut btree = BTreeMap::<K, V, _>::new(mem);
+
+        // All BTreeMap instances have the same struct layout regardless of K/V.
+        // Update this value if the struct layout changes.
+        assert_eq!(btree.heap_memory_used(), 52);
+
+        let base_used = btree.stable_memory_used();
+        let chunk_size = btree.allocator.chunk_size().get() as usize;
+
+        // Insert entries.
+        for i in 0..50_u32 {
+            btree.insert(K::build(i), V::build(i));
+        }
+        let chunks_after_insert = btree.allocator.num_allocated_chunks();
+        assert!(chunks_after_insert > 0);
+        assert_eq!(
+            btree.stable_memory_used(),
+            base_used + chunks_after_insert as usize * chunk_size
+        );
+        assert!(btree.stable_memory_used() <= btree.stable_memory_size());
+
+        // Remove all entries.
+        for i in 0..50_u32 {
+            btree.remove(&K::build(i));
+        }
+        assert_eq!(btree.allocator.num_allocated_chunks(), 0);
+        assert_eq!(btree.stable_memory_used(), base_used);
+    }
+
+    #[test]
+    fn memory_reporting_u32_u32() {
+        memory_reporting_for_type::<u32, u32>();
+    }
+
+    #[test]
+    fn memory_reporting_blob10_blob20() {
+        memory_reporting_for_type::<Blob<10>, Blob<20>>();
+    }
+
+    #[test]
+    fn memory_reporting_u32_unit() {
+        memory_reporting_for_type::<u32, ()>();
+    }
+
+    #[test]
+    fn memory_reporting_vec_u8_vec_u8() {
+        memory_reporting_for_type::<MonotonicVec32, MonotonicVec32>();
+    }
+
+    #[test]
+    fn memory_reporting_string_string() {
+        memory_reporting_for_type::<MonotonicString32, MonotonicString32>();
+    }
+
+    #[test]
+    fn memory_reporting_blob10_vec_u8() {
+        memory_reporting_for_type::<Blob<10>, MonotonicVec32>();
+    }
+
+    #[test]
+    fn height_empty() {
+        let mem = make_memory();
+        let btree = BTreeMap::<u32, (), _>::new(mem);
+        assert_eq!(btree.height(), 0);
+        assert_eq!(btree.height_approx(), 0);
+    }
+
+    #[test]
+    fn height_exact_vs_approx() {
+        let mem = make_memory();
+        let mut btree = BTreeMap::<u32, (), _>::new(mem);
+
+        // Insert items in batches and compare exact vs approximate height.
+        let test_sizes = [1, 5, 11, 12, 50, 100, 500, 1_000, 5_000, 10_000, 50_000, 100_000];
+
+        for &target in &test_sizes {
+            while btree.len() < target {
+                let i = btree.len() as u32;
+                btree.insert(i, ());
+            }
+
+            let exact = btree.height();
+            let approx = btree.height_approx();
+            let diff = (approx as i32) - (exact as i32);
+
+            assert!(
+                exact > 0,
+                "n={target}: exact height should be > 0 after inserts"
+            );
+            assert!(
+                diff.unsigned_abs() <= 1,
+                "n={target}: height_approx ({approx}) differs from \
+                 height ({exact}) by more than 1"
+            );
+        }
+
+        // Sanity: at 100k entries the tree should be reasonably short.
+        assert!(btree.height() <= 7);
+    }
 }
diff --git a/src/btreemap/allocator.rs b/src/btreemap/allocator.rs
index 68544599..229823ed 100644
--- a/src/btreemap/allocator.rs
+++ b/src/btreemap/allocator.rs
@@ -1,4 +1,5 @@
 use crate::{
+    mem_size::MemSize,
     read_struct,
     types::{Address, Bytes, NULL},
     write_struct, Memory,
@@ -45,6 +46,17 @@ pub struct Allocator<M: Memory> {
     memory: M,
 }
 
+impl<M: Memory> MemSize for Allocator<M> {
+    fn mem_size(&self) -> usize {
+        // Excludes `memory: M` — it's a handle to the backing store,
+        // not data owned by the allocator.
+        self.header_addr.mem_size()
+            + self.allocation_size.mem_size()
+            + self.num_allocated_chunks.mem_size()
+            + self.free_list_head.mem_size()
+    }
+}
+
 #[repr(C, packed)]
 #[derive(PartialEq, Debug)]
 struct AllocatorHeader {
@@ -225,17 +237,21 @@ impl<M: Memory> Allocator<M> {
         write_struct(&header, self.header_addr, &self.memory);
     }
 
-    #[cfg(test)]
-    pub fn num_allocated_chunks(&self) -> u64 {
+    pub(crate) fn num_allocated_chunks(&self) -> u64 {
         self.num_allocated_chunks
     }
 
-    // The full size of a chunk, which is the size of the header + the `allocation_size` that's
-    // available to the user.
-    fn chunk_size(&self) -> Bytes {
+    /// The full size of a chunk, which is the size of the header + the `allocation_size` that's
+    /// available to the user.
+    pub(crate) fn chunk_size(&self) -> Bytes {
         self.allocation_size + ChunkHeader::size()
     }
 
+    /// Returns the size of the allocator header in bytes.
+    pub(crate) fn header_size() -> Bytes {
+        AllocatorHeader::size()
+    }
+
     /// Destroys the allocator and returns the underlying memory.
     #[inline]
     pub fn into_memory(self) -> M {
diff --git a/src/btreemap/node.rs b/src/btreemap/node.rs
index 5daa0c40..89ec68c4 100644
--- a/src/btreemap/node.rs
+++ b/src/btreemap/node.rs
@@ -1,5 +1,6 @@
 use crate::{
     btreemap::Allocator,
+    mem_size::MemSize,
     read_address_vec, read_struct, read_to_vec, read_u32, read_u64,
     storable::Storable,
     types::{Address, Bytes},
@@ -18,7 +19,7 @@ use io::NodeReader;
 
 // The minimum degree to use in the btree.
 // This constant is taken from Rust's std implementation of BTreeMap.
-const B: usize = 6;
+pub(crate) const B: usize = 6;
 // The maximum number of entries per node.
 const CAPACITY: usize = 2 * B - 1;
 const LAYOUT_VERSION_1: u8 = 1;
@@ -36,6 +37,12 @@ pub enum NodeType {
     Internal,
 }
 
+impl MemSize for NodeType {
+    fn mem_size(&self) -> usize {
+        core::mem::size_of::<Self>()
+    }
+}
+
 pub type Entry<K> = (K, Vec<u8>);
 pub type EntryRef<'a, K> = (&'a K, &'a [u8]);
 
@@ -66,6 +73,17 @@ pub struct Node<K: Storable + Ord + Clone> {
     overflows: Vec<Address>,
 }
 
+impl<K: Storable + Ord + Clone + MemSize> MemSize for Node<K> {
+    fn mem_size(&self) -> usize {
+        self.address.mem_size()
+            + self.entries.mem_size()
+            + self.children.mem_size()
+            + self.node_type.mem_size()
+            + self.version.mem_size()
+            + self.overflows.mem_size()
+    }
+}
+
 impl<K: Storable + Ord + Clone> Node<K> {
     /// Loads a node from memory at the given address.
     pub fn load<M: Memory>(address: Address, page_size: PageSize, memory: &M) -> Self {
@@ -528,7 +546,7 @@ impl NodeHeader {
 
 /// A lazily-loaded object, which can be either an immediate value or a deferred reference.
 #[derive(Debug)]
-enum LazyObject<T> {
+enum LazyObject<T: Storable> {
     ByVal(T),
     ByRef {
         offset: Bytes,
@@ -537,7 +555,31 @@ enum LazyObject<T> {
     },
 }
 
-impl<T> LazyObject<T> {
+impl<T: Storable> LazyObject<T> {
+    /// Reports the serialized data size for loaded values, or just the
+    /// fixed fields for unloaded references. Uses `Storable::to_bytes()`
+    /// to measure ByVal — avoids requiring `T: MemSize`.
+    fn mem_size(&self) -> usize {
+        match self {
+            LazyObject::ByVal(value) => value.to_bytes().len(),
+            LazyObject::ByRef {
+                offset,
+                size,
+                loaded,
+            } => {
+                offset.mem_size()
+                    + size.mem_size()
+                    + if loaded.get().is_some() {
+                        *size as usize
+                    } else {
+                        0
+                    }
+            }
+        }
+    }
+}
+
+impl<T: Storable> LazyObject<T> {
     #[inline(always)]
     pub fn by_value(value: T) -> Self {
         LazyObject::ByVal(value)
@@ -582,6 +624,12 @@ type Blob = Vec<u8>;
 #[derive(Debug)]
 struct LazyValue(LazyObject<Blob>);
 
+impl MemSize for LazyValue {
+    fn mem_size(&self) -> usize {
+        self.0.mem_size()
+    }
+}
+
 impl LazyValue {
     #[inline(always)]
     pub fn by_value(value: Blob) -> Self {
@@ -605,9 +653,15 @@ impl LazyValue {
 }
 
 #[derive(Debug)]
-struct LazyKey<K>(LazyObject<K>);
+struct LazyKey<K: Storable>(LazyObject<K>);
 
-impl<K> LazyKey<K> {
+impl<K: Storable> MemSize for LazyKey<K> {
+    fn mem_size(&self) -> usize {
+        self.0.mem_size()
+    }
+}
+
+impl<K: Storable> LazyKey<K> {
     #[inline(always)]
     pub fn by_value(value: K) -> Self {
         Self(LazyObject::by_value(value))
@@ -647,6 +701,15 @@ impl Version {
     }
 }
 
+impl MemSize for Version {
+    fn mem_size(&self) -> usize {
+        match self {
+            Version::V1(page_size) => page_size.mem_size(),
+            Version::V2(page_size) => page_size.mem_size(),
+        }
+    }
+}
+
 /// The size of an individual page in the memory where nodes are stored.
 /// A node, if it's bigger than a single page, overflows into multiple pages.
 #[allow(dead_code)]
@@ -669,6 +732,15 @@ impl PageSize {
     }
 }
 
+impl MemSize for PageSize {
+    fn mem_size(&self) -> usize {
+        match self {
+            Self::Value(page_size) => page_size.mem_size(),
+            Self::Derived(derived) => derived.mem_size(),
+        }
+    }
+}
+
 /// A page size derived from the maximum sizes of the keys and values.
 #[derive(Debug, PartialEq, Copy, Clone, Eq)]
 pub struct DerivedPageSize {
@@ -682,3 +754,9 @@ impl DerivedPageSize {
         v1::size_v1(self.max_key_size, self.max_value_size).get() as u32
     }
 }
+
+impl MemSize for DerivedPageSize {
+    fn mem_size(&self) -> usize {
+        self.max_key_size.mem_size() + self.max_value_size.mem_size()
+    }
+}
diff --git a/src/btreemap/node/tests.rs b/src/btreemap/node/tests.rs
index ff1158ca..622dac1e 100644
--- a/src/btreemap/node/tests.rs
+++ b/src/btreemap/node/tests.rs
@@ -309,3 +309,70 @@ fn can_call_node_value_multiple_times_on_same_index() {
     let value2 = node.value(0, &mem);
     assert_eq!(value1, value2);
 }
+
+mod mem_size_tests {
+    use super::*;
+    use crate::mem_size::MemSize;
+
+    #[test]
+    fn lazy_value_by_value() {
+        // ByVal with a 5-byte blob: reports the serialized length.
+        let val = LazyValue::by_value(vec![1, 2, 3, 4, 5]);
+        assert_eq!(val.mem_size(), 5);
+    }
+
+    #[test]
+    fn lazy_value_by_ref_not_loaded() {
+        // ByRef before loading: offset (8) + size (4) = 12, no data.
+        let val = LazyValue::by_ref(Bytes::new(100), 42);
+        assert_eq!(val.mem_size(), 8 + 4);
+    }
+
+    #[test]
+    fn lazy_value_by_ref_loaded() {
+        // ByRef after loading: offset (8) + size (4) + data (42) = 54.
+        let val = LazyValue::by_ref(Bytes::new(100), 42);
+        val.get_or_load(|_, size| vec![0u8; size as usize]);
+        assert_eq!(val.mem_size(), 8 + 4 + 42);
+    }
+
+    #[test]
+    fn lazy_key_u32_by_value() {
+        // u32 serializes to 4 bytes.
+        let key = LazyKey::<u32>::by_value(42);
+        assert_eq!(key.mem_size(), 4);
+    }
+
+    #[test]
+    fn lazy_key_u32_by_ref_not_loaded() {
+        let key = LazyKey::<u32>::by_ref(Bytes::new(100), 4);
+        assert_eq!(key.mem_size(), 8 + 4);
+    }
+
+    #[test]
+    fn lazy_key_u32_by_ref_loaded() {
+        let key = LazyKey::<u32>::by_ref(Bytes::new(100), 4);
+        key.get_or_load(|_, _| 42u32);
+        assert_eq!(key.mem_size(), 8 + 4 + 4);
+    }
+
+    #[test]
+    fn lazy_key_vec_by_value() {
+        // Vec<u8> key with 10 bytes of data.
+        let key = LazyKey::<Vec<u8>>::by_value(vec![0u8; 10]);
+        assert_eq!(key.mem_size(), 10);
+    }
+
+    #[test]
+    fn lazy_key_vec_by_ref_not_loaded() {
+        let key = LazyKey::<Vec<u8>>::by_ref(Bytes::new(100), 10);
+        assert_eq!(key.mem_size(), 8 + 4);
+    }
+
+    #[test]
+    fn lazy_key_vec_by_ref_loaded() {
+        let key = LazyKey::<Vec<u8>>::by_ref(Bytes::new(100), 10);
+        key.get_or_load(|_, size| vec![0u8; size as usize]);
+        assert_eq!(key.mem_size(), 8 + 4 + 10);
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 5b5a98fc..1d685f29 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -8,6 +8,7 @@ pub mod file_mem;
 #[cfg(target_arch = "wasm32")]
 mod ic0_memory; // Memory API for canisters.
 pub mod log;
+mod mem_size;
 pub mod memory_manager;
 pub mod min_heap;
 pub mod reader;
diff --git a/src/mem_size.rs b/src/mem_size.rs
new file mode 100644
index 00000000..a12397a3
--- /dev/null
+++ b/src/mem_size.rs
@@ -0,0 +1,182 @@
+/// Estimates the in-process memory footprint of a value in bytes,
+/// covering both inline (stack) and heap-allocated data.
+///
+/// Reports the logical data size, not the physical layout. Alignment
+/// padding and allocator overhead are intentionally excluded — the
+/// goal is to measure how much memory the data itself occupies.
+///
+/// ## Performance
+///
+/// Primitives, strings, and fixed-size containers are always O(1).
+///
+/// Vectors of types with a known `ELEMENT_SIZE` are also O(1),
+/// using simple multiplication instead of traversal.
+///
+/// Types with a variable or unknown element size fall back to
+/// per-element iteration, which is O(n). Implement `ELEMENT_SIZE`
+/// for your fixed-size types to stay on the fast path.
+pub trait MemSize {
+    /// Fixed per-element size, if known at compile time.
+    /// When `Some`, `Vec<T>::mem_size()` uses `len * ELEMENT_SIZE` (O(1))
+    /// instead of iterating (O(n)). Defaults to `None`.
+    const ELEMENT_SIZE: Option<usize> = None;
+
+    /// Returns the estimated memory footprint of this value in bytes.
+    fn mem_size(&self) -> usize;
+}
+
+impl MemSize for () {
+    #[inline]
+    fn mem_size(&self) -> usize {
+        0
+    }
+}
+
+impl MemSize for u8 {
+    const ELEMENT_SIZE: Option<usize> = Some(std::mem::size_of::<u8>());
+
+    #[inline]
+    fn mem_size(&self) -> usize {
+        std::mem::size_of::<u8>()
+    }
+}
+
+impl MemSize for [u8] {
+    #[inline]
+    fn mem_size(&self) -> usize {
+        std::mem::size_of_val(self)
+    }
+}
+
+impl MemSize for u32 {
+    const ELEMENT_SIZE: Option<usize> = Some(std::mem::size_of::<u32>());
+
+    #[inline]
+    fn mem_size(&self) -> usize {
+        std::mem::size_of::<u32>()
+    }
+}
+
+impl MemSize for u64 {
+    const ELEMENT_SIZE: Option<usize> = Some(std::mem::size_of::<u64>());
+
+    #[inline]
+    fn mem_size(&self) -> usize {
+        std::mem::size_of::<u64>()
+    }
+}
+
+impl MemSize for &str {
+    #[inline]
+    fn mem_size(&self) -> usize {
+        self.as_bytes().mem_size()
+    }
+}
+
+impl<T: MemSize> MemSize for Vec<T> {
+    #[inline]
+    fn mem_size(&self) -> usize {
+        let elements_size = match T::ELEMENT_SIZE {
+            Some(el_size) => self.len() * el_size,
+            None => self.iter().map(|x| x.mem_size()).sum::<usize>(),
+        };
+        std::mem::size_of::<Self>() + elements_size
+    }
+}
+
+impl<A: MemSize, B: MemSize> MemSize for (A, B) {
+    #[inline]
+    fn mem_size(&self) -> usize {
+        self.0.mem_size() + self.1.mem_size()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_mem_size_unit() {
+        assert_eq!(().mem_size(), 0);
+    }
+
+    #[test]
+    fn test_mem_size_u8() {
+        assert_eq!(0_u8.mem_size(), 1);
+        assert_eq!(42_u8.mem_size(), 1);
+    }
+
+    #[test]
+    fn test_mem_size_u8_slice() {
+        let a: [u8; 0] = [];
+        assert_eq!(a.mem_size(), 0);
+        assert_eq!([1_u8].mem_size(), 1);
+        assert_eq!([1_u8, 2_u8].mem_size(), 2);
+    }
+
+    #[test]
+    fn test_mem_size_u32() {
+        assert_eq!(0_u32.mem_size(), 4);
+        assert_eq!(42_u32.mem_size(), 4);
+    }
+
+    #[test]
+    fn test_mem_size_u64() {
+        assert_eq!(0_u64.mem_size(), 8);
+        assert_eq!(42_u64.mem_size(), 8);
+    }
+
+    #[test]
+    fn test_mem_size_u8_vec() {
+        let base = std::mem::size_of::<Vec<u8>>();
+        assert_eq!(Vec::<u8>::from([]).mem_size(), base);
+        assert_eq!(Vec::<u8>::from([1]).mem_size(), base + 1);
+        assert_eq!(Vec::<u8>::from([1, 2]).mem_size(), base + 2);
+    }
+
+    #[test]
+    fn test_mem_size_str() {
+        assert_eq!("a".mem_size(), 1);
+        assert_eq!("ab".mem_size(), 2);
+    }
+
+    #[test]
+    fn test_mem_size_vec_with_element_size() {
+        // Vec<u32> uses the ELEMENT_SIZE fast path (Some(4)).
+        let base = std::mem::size_of::<Vec<u32>>();
+        assert_eq!(Vec::<u32>::new().mem_size(), base);
+        assert_eq!(vec![1_u32].mem_size(), base + 4);
+        assert_eq!(vec![1_u32, 2, 3].mem_size(), base + 12);
+    }
+
+    #[test]
+    fn test_mem_size_vec_without_element_size() {
+        type Blob = Vec<u8>;
+        // Vec<Blob> has ELEMENT_SIZE = None, falls back to per-element iteration.
+        let base = std::mem::size_of::<Vec<Blob>>();
+        let blob_base = std::mem::size_of::<Blob>();
+        assert_eq!(Vec::<Blob>::new().mem_size(), base);
+        // Each Blob reports size_of::<Blob>() + content_len.
+        assert_eq!(vec![Blob::from([1, 2])].mem_size(), base + blob_base + 2);
+        assert_eq!(
+            vec![Blob::from([1]), Blob::from([2, 3])].mem_size(),
+            base + 2 * blob_base + 3
+        );
+    }
+
+    #[test]
+    fn test_mem_size_tuple() {
+        // Measures logical data size, not physical layout.
+        // (u32, u64) = 4 + 8 = 12 bytes (padding excluded).
+        assert_eq!((1_u32, 2_u64).mem_size(), 4 + 8);
+    }
+
+    #[test]
+    fn test_element_size_constants() {
+        assert_eq!(<u8 as MemSize>::ELEMENT_SIZE, Some(1));
+        assert_eq!(<u32 as MemSize>::ELEMENT_SIZE, Some(4));
+        assert_eq!(<u64 as MemSize>::ELEMENT_SIZE, Some(8));
+        // Vec<u8> has no fixed element size.
+        assert_eq!(<Vec<u8> as MemSize>::ELEMENT_SIZE, None);
+    }
+}
diff --git a/src/types.rs b/src/types.rs
index 0c9bbf7f..3a3aacc9 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -1,3 +1,4 @@
+use crate::mem_size::MemSize;
 use core::ops::{Add, AddAssign, Div, Mul, Rem, Sub, SubAssign};
 
 pub const NULL: Address = Address(0);
@@ -53,6 +54,16 @@ impl AddAssign<Bytes> for Address {
     }
 }
 
+impl MemSize for Address {
+    const ELEMENT_SIZE: Option<usize> = Some(std::mem::size_of::<Self>());
+
+    #[inline]
+    fn mem_size(&self) -> usize {
+        let val = self.0;
+        val.mem_size()
+    }
+}
+
 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Ord, Eq)]
 pub struct Bytes(u64);
 
@@ -140,6 +151,16 @@ impl SubAssign<Bytes> for Bytes {
     }
 }
 
+impl MemSize for Bytes {
+    const ELEMENT_SIZE: Option<usize> = Some(std::mem::size_of::<Self>());
+
+    #[inline]
+    fn mem_size(&self) -> usize {
+        let val = self.0;
+        val.mem_size()
+    }
+}
+
 impl Bytes {
     pub const fn new(val: u64) -> Self {
         Self(val)