diff --git a/src/transaction.js b/src/transaction.js
index c195da3..8132bd2 100644
--- a/src/transaction.js
+++ b/src/transaction.js
@@ -325,18 +325,6 @@ Transaction.prototype.validateInput = function(index, prevOutScript, pubKey, DER
   return pubKey.verify(hash, signature)
 }
 
-Transaction.feePerKb = 20000
-Transaction.prototype.estimateFee = function(feePerKb){
-  var uncompressedInSize = 180
-  var outSize = 34
-  var fixedPadding = 34
-
-  if(feePerKb == undefined) feePerKb = Transaction.feePerKb;
-  var size = this.ins.length * uncompressedInSize + this.outs.length * outSize + fixedPadding
-
-  return feePerKb * Math.ceil(size / 1000)
-}
-
 function TransactionIn(data) {
   assert(data.outpoint && data.script, 'Invalid TxIn parameters')
   this.outpoint = data.outpoint
diff --git a/src/wallet.js b/src/wallet.js
index 4410b36..4915d68 100644
--- a/src/wallet.js
+++ b/src/wallet.js
@@ -237,10 +237,13 @@ function Wallet(seed, network) {
     return sortByValueDesc
   }
 
-  function estimateFeePadChangeOutput(tx){
+  var feePerKb = 20000
+  function estimateFeePadChangeOutput(tx) {
     var tmpTx = tx.clone()
     tmpTx.addOutput(getChangeAddress(), 0)
-    return tmpTx.estimateFee()
+
+    var byteSize = tmpTx.toBuffer().length
+    return feePerKb * Math.ceil(byteSize / 1000)
   }
 
   function getChangeAddress() {
diff --git a/test/transaction.js b/test/transaction.js
index b2c8b92..8cf2366 100644
--- a/test/transaction.js
+++ b/test/transaction.js
@@ -194,28 +194,6 @@ describe('Transaction', function() {
         assert.equal(validTx.validateInput(0, script, key.pub, sig), true)
       })
     })
-
-    describe('estimateFee', function() {
-      it('works for fixture tx 1', function() {
-        var tx = Transaction.fromHex(fixtureTx1Hex)
-        assert.equal(tx.estimateFee(), 20000)
-      })
-
-      it('works for fixture big tx', function() {
-        var tx = Transaction.fromHex(fixtureTxBigHex)
-        assert.equal(tx.estimateFee(), 60000)
-      })
-
-      it('allow feePerKb to be passed in as an argument', function() {
-        var tx = Transaction.fromHex(fixtureTx2Hex)
-        assert.equal(tx.estimateFee(10000), 10000)
-      })
-
-      it('allow feePerKb to be set to 0', function() {
-        var tx = Transaction.fromHex(fixtureTx2Hex)
-        assert.equal(tx.estimateFee(0), 0)
-      })
-    })
   })
 
   describe('signInput', function() {