# How long does it take on average to receive one confirmation? Is it still reversible?

Hi! Based on your experience, how long does it take to receive one confirmation for any given transaction which has payed the standard miner's fee? Is it still reversible?

Thanks!

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If a merchant or trader will be accepting payment on 0 confirmations (or even one or two confirmations), then there is a recommended configuration to lessen the risk of being defrauded due to a race attack. –  Stephen Gornick Jan 31 '13 at 2:51

A Bitcoin transaction, by design, will get one confirmation after an average of 10 minutes. Even before a confirmation has been received, a transaction is generally irreversible.

If you were to send a second (double-spend) transaction, using the same inputs as a transaction you've previously sent, I suppose there might be some custom-developed nodes that would give it priority if the transaction fee was higher than the first transaction. However, I believe most nodes would reject the second transaction.

If one of these (corrupt?) custom-developed nodes was to solve a block including the second transaction, my understanding is that the network would accept the block and thus accept the second transaction. This question has been asked separately, here: Does any pool accept higher-fee transactions of a double spend, instead of the earlier one?

However, it's worth mentioning that standard nodes will not relay the second transaction.

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However you could deliver at the same time two different transactions to two different standard nodes. –  Lohoris Jan 28 '13 at 16:02
This is incorrect. The average target time of 10 minutes means that the average waiting time for a single confirmation is 5 minutes. –  runeks Sep 5 '14 at 17:02
@runeks, you're wrong. There's an explanation here from one of the core Bitcoin developers: bitcointalk.org/index.php?topic=5521.0 –  Highly Irregular Sep 6 '14 at 0:16
@HighlyIrregular I think you are misinterpreting that post. It's physically impossible for the mean time between two generations to be ~600 seconds, and the average duration -- from any random point in time -- to the next generation to be equal. Think about it this way: if a bus departs every 10 minutes, and you arrive at the bus stop at a random time, what's the average amount of time you have to wait? 5 minutes. Remember, the average time between two generations, and the average waiting period until the next generation are two different figures. –  runeks Sep 6 '14 at 11:02
@runeks Assuming the hashrate is constant and the difficulty exactly matches it, the expected time until the next block is always 10 minutes, regardless of how long you have waited so far. –  Pieter Wuille Jul 18 at 18:09

simply looking at this chart tells you that average transaction confirmation time is not 10 minutes (block confirmation is 10min)

https://blockchain.info/charts/avg-confirmation-time

https://www.quandl.com/data/BCHAIN/ATRCT-Bitcoin-Average-Transaction-Confirmation-Time

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While the hash rate for the network is increasing, that would be expected. blockchain.info/charts/hash-rate –  Highly Irregular Jul 19 at 8:25

yes, its ok, The second confirm and beyond will obviously have the full 10 min average block time wait time however. simply looking at this chart tells you that average transaction confirmation time is not 10 minutes (block confirmation is 10min)

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So the first confirmation will on average be faster than the second because you wont need to wait the full 10 min's for the block to be mined as your transaction will be placed in a block while the mining process of the block has already started. The second confirm and beyond will obviously have the full 10 min average block time wait time however.

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This is wrong. Mining doesn't make progress; the odds of there being a block in the next 30 seconds are exactly the same no matter how long ago the last block was. –  Nick ODell Jul 15 at 3:43
Nick is correct, you can find a comprehensive explanation here: The expected time until the next block is always 10 minutes. I'm also assuming that the asker wasn't only inquiring about the block interval, but also how many blocks it would take until his transaction is included in one (because it doesn't necessarily have to make it into the next one). –  Murch Jul 15 at 18:02

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