What is block time?
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 4 min
In short
Block time is the interval between new blocks. Bitcoin targets roughly ten minutes; Ethereum runs on fixed 12-second slots. This single number shapes both how quickly a payment is confirmed and how much traffic the chain can carry.
Key points
- The target interval at which blocks are added
- Bitcoin aims for about ten minutes; Ethereum uses 12-second slots
- Shorter times confirm faster but produce more forks
- Actual intervals scatter around the target
Definition
The time between successive blocks being added to a chain. The protocol sets a target and the observed intervals vary around it.
Bitcoin targets one block roughly every ten minutes and holds that average through automatic difficulty adjustment. Ten minutes is only a mean, though: a block can appear in one minute or take more than thirty. Mining is a probabilistic search, so the spacing is never regular.
Since moving to proof of stake, Ethereum runs on a fixed rhythm of 12-second slots. Each slot has an assigned proposer, and if that proposer stays silent the slot is simply empty and the chain moves on. Observed gaps are therefore multiples of 12 seconds.
Shorter block times confirm payments faster but make it likelier that a new block is produced before the previous one has reached every node, which multiplies temporary forks. Bitcoin's long interval is a deliberate choice to leave slack for propagation delay.
Watch out for
- · Ten minutes is not a delivery promise — when blocks are full, low-fee transactions wait many rounds
- · One block is not finality, and the number of confirmations required differs from service to service