Every 2,016 blocks, about two weeks, Bitcoin resets mining difficulty so blocks average 10 minutes again. Learn the formula and the limits.
Keeping time
If more miners join, blocks would come faster. If miners leave, slower. To keep the average at 10 minutes, Bitcoin recalculates difficulty every 2,016 blocks, about two weeks.
The formula
new target = old target × (actual time for 2,016 blocks ÷ 20,160 minutes)- Took 12 days instead of 14? Target shrinks by 12/14: about 17% harder.
- Took 16 days? Target grows by 16/14: about 12.5% easier.
- A single adjustment can't change difficulty by more than a factor of 4 either way.
Why it matters
- Predictable supply: the halving stays roughly every four years.
- Self-correcting: if a large part of hash power suddenly disappears, blocks slow down for at most one period, then difficulty drops.
When is the next adjustment?
Take the current height, divide by 2,016 and round up to the next whole number: that multiple of 2,016 is the next adjustment height. For example, after block 973,000 the next is 973,728 (2,016 × 483).
Famous adjustments
In mid-2021, after a large share of mining shut down in China, difficulty fell by about 28% in a single adjustment, one of the biggest drops ever, and block times recovered within weeks.
Key takeaways
- Difficulty adjusts every 2,016 blocks (about two weeks).
- It scales with how long the last 2,016 blocks actually took.
- Each adjustment is capped at 4× in either direction.
Common questions
When is the next difficulty adjustment?
At the next block height that is a multiple of 2,016.
Can difficulty go down?
Yes, whenever blocks came slower than 10 minutes on average in the previous period.
How often does Bitcoin difficulty change?
Every 2,016 blocks, roughly every two weeks.
What happens if many miners leave at once?
Blocks slow down until the next adjustment, which then lowers difficulty by up to a factor of 4.