Sending from Coinbase to Blockchain wallet. Numbers explained?

1

I recently sent .9 BTC from my Coinbase account to a Blockchain.info wallet, but the numbers I see are confusing. According to my Blockchain app, the transaction was for .90130821 BTC, with a fee of .0001 BTC (for the miners, I get that). The .9 BTC made it to my wallet, but the remaining .00120821 went somewhere else. Because of this, I have three questions...

1) Why is the transaction amount more than the specific .9 BTC I wanted to send?

2) How was that amount (.00130821 BTC) chosen?

3) Where did the .00120821 BTC get sent?

This photo may help...

doffing81

Posted 2015-12-21T22:23:55.867

Reputation: 474

possible duplicate of How does change work in a bitcoin transaction?

– Murch – 2015-12-21T22:27:38.700

All I got from that was a generalization of "change." – doffing81 – 2015-12-21T22:37:24.683

Sorry, actually, this one is probably a better match: Why are there two transaction outputs when sending to one address?

– Murch – 2015-12-21T22:42:05.737

Answers

1

Unspent transaction output (UTXO) can only be spent in full, so if they don't match the amount you are trying to send exactly the rest will be sent back to yourself.

Therefore I assume that you had a single UTXO of the size 0.90130821 BTC in your wallet. When it was spent, the remainder was sent to a change address in your own wallet.

Murch

Posted 2015-12-21T22:23:55.867

Reputation: 41 609

Asked: 2015-12-21T22:23:55.867

Viewed: 2 771 times

Active: 2015-12-21T22:40:46.013