Guide
Bitcoin's 21 Million Cap: Why It Can't Be Increased and the Last Coin
Bottom line: 21 million coins, un-increasable by code
Bitcoin's total supply is fixed at about 21 million coins. This rule is written into the software and cannot be inflated the way a central bank can print money. It is one of the most important designs underpinning Bitcoin's scarcity.
Key takeaways
- The supply cap is ~21 million coins, fixed in code and not increasable.
- New issuance halves about every four years via the halving, slowly approaching the cap.
- The last fraction of a coin is projected to be issued around 2140.
- After the cap is reached, miners are paid mainly by transaction fees.
Why have a cap at all?
Fiat money supply expands or contracts with policy. Bitcoin was designed from the start with a fixed cap to preserve scarcity and avoid open-ended inflation. Because supply is fixed, the idea is that value can hold up as demand grows. For how that ties into value, see why Bitcoin has value.
How the cap is approached
New coins are paid as the mining reward, and that amount halves at each halving.
| Period | New issuance per block |
|---|---|
| 2009– | 50 BTC |
| 2012– | 25 BTC |
| 2016– | 12.5 BTC |
| 2020– | 6.25 BTC |
| Apr 2024– | 3.125 BTC |
Because the issuance rate falls geometrically, the total converges toward 21 million.
The last coin and "lost" BTC
The reward becomes vanishingly small, and the last fraction of a bitcoin is projected to be mined around 2140, after which miners earn from transaction fees alone. Note that a significant amount of bitcoin is thought to be permanently lost to forgotten keys, so the truly spendable supply is likely below 21 million.
FAQ
Q. Is it really capped at 21 million? A. Yes. It is fixed in code, and changing it would require near-impossible agreement across the whole network.
Q. Does mining stop once the cap is reached? A. No. New issuance ends, but transaction fees become the reward.
Q. Is it exactly 21 million? A. It falls slightly short in practice, but "about 21 million" is the right understanding.
Q. What's the benefit of a cap? A. It preserves scarcity and avoids open-ended monetary inflation.
Sources
- Bitcoin whitepaper: https://bitcoin.org/bitcoin.pdf
- Controlled supply (Bitcoin Wiki): https://en.bitcoin.it/wiki/Controlled_supply
Not investment advice
This article is for educational purposes only and is not investment advice. Bitcoin is volatile and carries risks including loss and theft. Do your own research and only use money you can afford to lose. Tax and regulation can change — always confirm with the official primary source.
Sources
FAQ
- Is it really capped at 21 million?
- Yes. It is fixed in code, and changing it would require near-impossible agreement across the whole network.
- Does mining stop once the cap is reached?
- No. New issuance ends, but transaction fees become the reward.
- When is the last coin mined?
- Issuance keeps halving, so the last fraction is projected around 2140.
This article is informational only and is not financial, investment, or trading advice. Prices are reference snapshots and may be outdated. Always do your own research.
