The 21 million cap
Bitcoin's supply cap: there will never be more than 21 million coins.
In plain words
New bitcoin exists only as mining rewards, and the reward halves about every four years. Sum the whole schedule: just under 21 million coins, the last sliver near 2140. The cap is not a promise. Promises need someone to keep them. It is a rule every node enforces — and changing it would mean convincing nearly everyone to act against their own interest.
Why it matters
- Absolute scarcity is new to this world: even gold's supply grows every year.
- No printing. No exceptions. That is what makes hard money hard.
- Enforced by users' nodes, entrusted to no 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