<p>The transaction fee calculated for the transaction by fundrawtransaction cannot actually predict the transaction's final size. This is because signatures are not fixed in length and can be smaller than what is predicted. However, in order to be sure enough fee is paid, fundrawtransaction will always assume the maximum signature size. This means that sometimes the signature will end up being smaller which means that you end up overpaying a little bit in fees. The feerate will be higher because the fee has stayed the same but the size of the transaction is smaller than predicted.</p>

CC BY-SA 4.0
2018-07-17T05:53:32.567Z
Thank you for answer. I understand this is not the good way to set a fee?
Oliver
CC BY-SA 4.0
2018-07-17T06:24:49.730Z
That depends, what "good" means for you. I acknowledge, it may not be the optimal way to define fees, in the sense that one can minimize/maximize fees ...
pebwindkraft
CC BY-SA 4.0
2018-07-16T21:06:09.627Z
2018-07-16T21:06:09.627Z
Ava Chow
<p>Create a raw transaction <code>createrawtransaction</code> (transactions, vouts, amount and where to send) 
then specify the commission for the miners <code>fundrawtransaction</code> <code>feeRate</code> But when I start checking or signing and sending, the commission becomes bigger .... What is it connected with? 
p.s sorry for my english :)</p>

<bitcoin-core>
Bitcoin rawtransaction fee
Oliver
# Bitcoin rawtransaction fee

(Asked by: username_0 on 2018-07-16)

Create a raw transaction `createrawtransaction` (transactions, vouts, amount and where to send)
then specify the commission for the miners `fundrawtransaction` `feeRate` But when I start checking or signing and sending, the commission becomes bigger .... What is it connected with?
p.s sorry for my english :)

**Tags:** bitcoin-core


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## 1 answers

### Answer by username_1 on 2018-07-16. Score: 2 | Accepted answer

The transaction fee calculated for the transaction by fundrawtransaction cannot actually predict the transaction's final size. This is because signatures are not fixed in length and can be smaller than what is predicted. However, in order to be sure enough fee is paid, fundrawtransaction will always assume the maximum signature size. This means that sometimes the signature will end up being smaller which means that you end up overpaying a little bit in fees. The feerate will be higher because the fee has stayed the same but the size of the transaction is smaller than predicted.

> **Comments:**
> **username_0**: Thank you for answer. I understand this is not the good way to set a fee?  
> **username_2**: That depends, what "good" means for you. I acknowledge, it may not be the optimal way to define fees, in the sense that one can minimize/maximize fees ...  

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