How to know which adress was used for sending BTCs when i send them?

[forzendiablo]

thats part of BTC i dont understand after all this years.
i have windows qt and setup 10 payment adresses there.
to each one of them i send 1 BTC, so each adress holds 1BTC but i only see total 10BTC on the wallet.

now tircky part comes - i send out 1,2BTC in 1 transaction and 1,9BTC in second.

what adresses will be used for "from" in this case [2 different or 1 same?]
which of adresses on blockchain will show with coins missing.

let me know as i totally dont get this part of trackign adresses.

[deepceleron]

Bitcoin uses previous payments from your wallet in a way that would minimize change.

You need to understand change a bit. Although I should write a longer explanation of change, this covers it briefly: http://we.lovebitco.in/how-bitcoin-works/transactions/

If you received payments of 1, 3, 7, and 8 bitcoin previously, and send someone 9 BTC, the 8 and 1 bitcoin balances would be used.

Alternately, if you sent someone 6 BTC, the 7 BTC payment would be used, and 1 BTC of change would come back to you in a new address not shown in your wallet. If you then spend another 2 BTC, 1 BTC + 1 BTC (change) would be used.

Due to change, the "from" addresses will likely include ones your client does not show to you. For this reason, if you look up a transaction ID on a blockchain explorer site, you may see addresses you didn't even know were yours.

Bitcoin hides all the behind-the-scenes stuff from you because it would take some education to understand it all. If you do not want to have addresses potentially tied to each other, you would need separate wallets, or need to manually construct transactions (which is an advanced topic).

[forzendiablo]

thanx a lot now i understand a bit more.

so transactions are not really anonymous because my whole wallet can be tracked.

to untrack it i would need to send to ie me -> exchange -> other installed wallet

is that right or also not enough ?

[Newar]

[...]

to untrack it i would need to send to ie me -> exchange -> other installed wallet

is that right or also not enough ?

Yes, as long as you trust the exchange, however 100% anonymity is not guaranteed with that method

[Dare]

If you'd like to see which addresses were used for a transaction of yours after the fact, just copy the transaction ID (Bitcoin Core: Transactions -> Right-click transaction in question -> Copy transaction ID) and paste it into blockchain.info's search field (or your block explorer of choice; any will work). That will show you all of the details of the transaction, including the sources of the coins involved and their destinations (which will probably only consist of the address you sent to and the change address).