The 21 million cap
Bitcoin's supply cap: there will never be more than 21 million coins.
In plain words
New bitcoin appears only as the reward for mining a block, and that reward halves about every four years. Add up the whole schedule and it stops just under 21 million coins, with the last bit arriving around 2140. The cap isn't a company's promise. It's a rule every node enforces. Changing it would mean convincing nearly everyone to run new software — against their own interest.
Why it matters
- Absolute scarcity is new: even gold's supply grows every year.
- No printing, no exceptions — the cap is what makes bitcoin hard money.
- Enforced by users' nodes, not trusted to any authority.
Numbers that matter
- 210,000 blocks — between halvings, about four years.
- ~2140 — when the last fraction is mined.
- >95% — of all bitcoin already exists.
Not to be confused with
- "Exactly 21 million" — it technically tops out slightly below, at 20,999,999.97.
Go deeper
Updated 2026-07-29