diff --git a/lib/model/txproposal.js b/lib/model/txproposal.js
index f6dd382..2697c4c 100644
--- a/lib/model/txproposal.js
+++ b/lib/model/txproposal.js
@@ -228,7 +228,13 @@ TxProposal.prototype.getRawTx = function() {
 };
 
 TxProposal.prototype.getEstimatedSizeForSingleInput = function() {
-  return this.requiredSignatures * 72 + this.walletN * 36 + 44;
+  switch (this.addressType) {
+    case Constants.SCRIPT_TYPES.P2PKH:
+      return 147;
+    default:
+    case Constants.SCRIPT_TYPES.P2SH:
+      return this.requiredSignatures * 72 + this.walletN * 36 + 44;
+  }
 };
 
 TxProposal.prototype.getEstimatedSize = function() {