So, after understanding how to create and send raw transactions on the basis of 'How to send from many bitcoin addresses to one bitcoin address?', in practice I still struggle with transaction fees. For example, I do the following in order to calculate the size of an hex-encoded transaction:

hex_raw_transaction = createrawtransaction(...)
hex_raw_transaction = signrawtransaction(hex_raw_transaction)
byte[] size = HexStringToByteArray(hex_raw_transaction)
int transaction_size = size.Length

Is that a correct way to determinate the transaction size? (Regarding to https://en.bitcoin.it/wiki/Transaction_fees)?

Is it correct that the transaction fee is set by the unassigned amount in the outputs?

For example, if I have 1 BTC in one address and send the 0.65 BTC to a second address and 0.3495 BTC as change to the first

//The fee will be: 
fee = 1 - (0.65 + 0.3495)  //= 0.0005 btc

is it correct that the fee will be 0.0005 BTC?


Here is a great answer on how to calculate the transaction size before sending. (Make sure to read the final edit.)

As for the fee, you've got it right: whatever amount from the inputs is NOT sent to other addresses, becomes the transaction fee for the miners.

  • Yes it exactly the same value size of transaction if we use bitcoind getrawtransaction command, e.g. bitcoind getrawtransaction d9804de366aa4c2a01565c3a3c8aa2ea20baafc276dc875f80b9044841205333 return 15522 length of hex-string, so in real bytes it will be 7761 whcih is actual size of transaction – Arsenius Sep 17 '13 at 15:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.