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I am trying to get real fee per trasnaction.

So I have an account whit balance 0.06940000 and have a second account with balance 0.00000000.

To get current fee I have run the command

bitcoin-cli getmempoolinfo

and got the mempoolminfee = 0.00001000. I thought that when I send the 0.06939000 in my account rest balance will 0.00000000. but I got 0.00004860. Actually the fee was 0.0000514.

general question is WhY ?

Please tell me to understand how is fees working!

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What getmempoolinfo is returning is not the minimum fee to send a transaction, but the minimum rate per kilobyte to send a transaction. Your bitcoin client will take the configured fee and multiply it by the size of the transaction in kilobytes to calculate the actual transaction fee.

The size of a transaction is somewhat difficult to compute (for a person) because it requires understanding the number of inputs that are required to fulfil the transaction, the number of outputs (primary recipients + change address), and the targeted transaction fee (since appropriate fees could eliminate the need for a change address).

There are online fee calculators out there you can use to estimate these, but it is still difficult to completely empty a wallet with a known fee using the straight bitcoin client.

  • Is there a way to get fee before sending transaction ? – Yur Gasparyan Oct 1 '18 at 13:03
  • No, but if all you are looking to do is empty a wallet, you can pass an argument to sendtoaddress which will take the fee out of the sent amount rather than the wallet you're sending from--you will receive less bitcoin than you "sent", but you will be able to empty the wallet. See argument #5 for sendtoaddress: bitcoin.org/en/developer-reference#sendtoaddress – Motoma Oct 1 '18 at 13:09
  • thanks! but what when i want to send bitcoins from specific account to address? – Yur Gasparyan Oct 1 '18 at 13:16
  • Again, if you want to remove a specific amount from the sending address, you set that 5th argument to true. If you want a specific amount to be received by the recipient address, you leave it set to false. – Motoma Oct 1 '18 at 13:31

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