diff --git a/src/block.js b/src/block.js
index 22449fd..18b49c7 100644
--- a/src/block.js
+++ b/src/block.js
@@ -127,12 +127,18 @@ class Block {
   hasWitness() {
     return anyTxHasWitness(this.transactions);
   }
-  byteLength(headersOnly) {
+  weight() {
+    const base = this.byteLength(false, false);
+    const total = this.byteLength(false, true);
+    return base * 3 + total;
+  }
+  byteLength(headersOnly, allowWitness = true) {
     if (headersOnly || !this.transactions) return 80;
     return (
       80 +
       varuint.encodingLength(this.transactions.length) +
-      this.transactions.reduce((a, x) => a + x.byteLength(), 0)
+      // @ts-ignore using the __byteLength private method on Transaction
+      this.transactions.reduce((a, x) => a + x.__byteLength(allowWitness), 0)
     );
   }
   getHash() {
diff --git a/test/block.spec.ts b/test/block.spec.ts
index 0f74392..e93420c 100644
--- a/test/block.spec.ts
+++ b/test/block.spec.ts
@@ -48,6 +48,11 @@ describe('Block', () => {
         assert.strictEqual(block.bits, f.bits);
         assert.strictEqual(block.nonce, f.nonce);
         assert.strictEqual(!block.transactions, f.hex.length === 160);
+        if (f.size && f.strippedSize && f.weight) {
+          assert.strictEqual(block.byteLength(false, true), f.size);
+          assert.strictEqual(block.byteLength(false, false), f.strippedSize);
+          assert.strictEqual(block.weight(), f.weight);
+        }
       });
     });
 
diff --git a/test/fixtures/block.json b/test/fixtures/block.json
index c60685e..8ea521c 100644
--- a/test/fixtures/block.json
+++ b/test/fixtures/block.json
@@ -133,7 +133,10 @@
       "prevHash": "8980ebb11236bacc66c447d5ad961bc546c0f9cc385a08000000000000000000",
       "timestamp": 1537429727,
       "valid": true,
-      "version": 536870912
+      "version": 536870912,
+      "size": 2355,
+      "strippedSize": 2209,
+      "weight": 8982
     }
   ],
   "invalid": [
diff --git a/ts_src/block.ts b/ts_src/block.ts
index cf4ed51..0792edf 100644
--- a/ts_src/block.ts
+++ b/ts_src/block.ts
@@ -148,13 +148,20 @@ export class Block {
     return anyTxHasWitness(this.transactions!);
   }
 
-  byteLength(headersOnly?: boolean): number {
+  weight(): number {
+    const base = this.byteLength(false, false);
+    const total = this.byteLength(false, true);
+    return base * 3 + total;
+  }
+
+  byteLength(headersOnly?: boolean, allowWitness: boolean = true): number {
     if (headersOnly || !this.transactions) return 80;
 
     return (
       80 +
       varuint.encodingLength(this.transactions.length) +
-      this.transactions.reduce((a, x) => a + x.byteLength(), 0)
+      // @ts-ignore using the __byteLength private method on Transaction
+      this.transactions.reduce((a, x) => a + x.__byteLength(allowWitness), 0)
     );
   }
 
diff --git a/types/block.d.ts b/types/block.d.ts
index d77bb1b..7d8309c 100644
--- a/types/block.d.ts
+++ b/types/block.d.ts
@@ -15,7 +15,8 @@ export declare class Block {
     getWitnessCommit(): Buffer | null;
     hasWitnessCommit(): boolean;
     hasWitness(): boolean;
-    byteLength(headersOnly?: boolean): number;
+    weight(): number;
+    byteLength(headersOnly?: boolean, allowWitness?: boolean): number;
     getHash(): Buffer;
     getId(): string;
     getUTCDate(): Date;