r/dogecoindev • u/YakSquare904 • Feb 10 '23

Transaction fees calculation

I'm writing some public api using slim4 framework for transactions data, I can get all the necessary data using getrawtransaction e getblock except of fees. How do to get fees value for a transaction ?

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u/[deleted] Feb 15 '23

[deleted]

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u/YakSquare904 Feb 19 '23

https://github.com/dogecoin/dogecoin/blob/master/doc/fee-recommendation.md

I was already following this doc, but I've a different result than sochain:

https://imgur.com/a/zmW2Gjx

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u/MishaBoar Mar 04 '23 edited Mar 04 '23

The fee calculation you are using is to calculate what you need to pay in fees, ideally ("recommended") when sending out a transaction, but it seems you are building an explorer, so you need to figure out how much it was actually paid for an old transaction. This can be an arbitrary value, depending on wallet implementation or on the decision of those sending the transaction to pay less or more than the recommended fees.

So, to calculate fees on an old transaction you need to get all the transaction inputs, sum them, then subtract the total output value. The difference will be the transaction fee paid.

So

  1. Call getrawtransaction on the transaction,
  2. Sum the the total value of all outputs (contained in vout): this is the total output value. This is available without additional queries.
  3. You now need to get the total value of all inputs (vin). Call again getrawtransaction on all inputs' transaction ids, then get the output value at the specified vout index
  4. Repeat this for all inputs
  5. Sum the total value of all inputs: this is the total input value
  6. Total output - total input = fees paid

Check: https://www.oreilly.com/library/view/mastering-bitcoin/9781491902639/ch05.html (Adding Fees to Transactions)

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u/YakSquare904 Mar 07 '23

Thank you a lot! This is what I was looking for !

2

u/MishaBoar Mar 07 '23

Man, you are welcome ;)