Bitcoin Confirmations Explained

Confirmations, in Plain Terms

A Bitcoin transaction only truly settles after it is included in a block. Once it has been confirmed in that way, it has received one confirmation. Each additional block mined on top of the one that first included it adds one more confirmation, increasing the security against double spending. The amount of risk dropped with each additional confirmation, but the trade-off is still a complex issue.

Most users will never have to worry about double spending unless they are dealing with highly high-value Bitcoin transactions. And the probability of a double spend does decrease significantly as more confirmations are received. But it does exist.

Why Wait Times Vary

Because Bitcoin block production targets a new block every 10 minutes on average. Each new block adds a confirmation to the transactions within it. But that 10-minute average is exactly that: an average, not a guarantee.

finds that a Bitcoin block is actually created once every 9 minutes and 38 seconds on average.

So precise wait times are hard to pin down in the general case. Under the 10-minute average, 6 confirmations represent roughly an hour of wait time. But a Bitcoin transaction might be confirmed in only 30 minutes, or an hour and a half, depending on how the timing works out.

Why Exchanges Ask for Different Counts

Because each receiving platform sets its own acceptable confirmation count based on its risk tolerance and double-spend exposure. A transaction with no confirmations is still sitting in the mempool: not included in a block. Zero-confirmation transactions are basically free to be double spent.

One confirmation means it's included in a block. That makes it much harder to double-spend, but with enough hash power, double spending might still be possible.

Six confirmations are conventional because that roughly represents hour of wait time, but any receiving platform, especially for lower-value transactions, might accept fewer.

Bitcoin, Ethereum, and Finality

Bitcoin has probabilistic confirmations which can never be guaranteed to have matched the 10 minute average. Ethereum, on the other hand, has checkpoint-based finality.

For Ethereum, a transaction has protocol-level finality after two consensus epochs - approximately 12.8 minutes since the transaction initially being included in a block. Confirmation is one thing, and network-accepted finality is another.

What to Check in a Block Explorer

When checking a Bitcoin transaction's status in a block explorer, first look for the transaction's "included in block" height and then look for the confirmation count. The confirmation count shows how many additional blocks have been stacked on top of the one the transaction was first included in.

In summary

When asking how many Bitcoin confirmations a transaction needs, the most important thing to check first is the receiving platform's own rules on how many confirmations it accepts. Bitcoin provides confirmations by adding blocks on top of the transaction, but it's the receiving wallet or exchange that decides how many it wants to see.