Why 21 million?
There will only ever be up to 21 million bitcoin (just under, at 20,999,999.9769). That limit is written into the rules every node enforces, and changing it would need almost everyone running the network to agree to make their own coins worth less. That is why most people treat it as permanent.
New coins enter circulation as the reward miners earn for each block. Every 210,000 blocks, roughly every four years, that reward is cut in half. This is called the halving. The last bitcoin is expected to be mined around the year 2140.
Bitcoin's supply schedule is public and fixed in code. Anyone can check how many coins exist, and how many will exist on any future date. About 20.1 million had been issued by 31 October 2026 (blockchain.com).
Scarcity on its own does not guarantee a price. The price still moves with demand, and it can fall a long way. But a fixed supply is the main reason people call Bitcoin hard money.
Key takeaways
- The cap of 21 million is enforced by every node on the network.
- The miner reward halves about every four years.
- A fixed supply does not stop the price falling in the short term.
Not financial advice. These lessons are general education only. Bitcoin prices can swing hard. Never put in more than you can afford to lose, and do your own research.