21 million (Bitcoin’s supply cap)

Under the network’s rules, there will never be more than just under 21 million BTC. Unlike the euro or the dollar, there is no central bank that can create additional units.

Where the limit comes from

It follows from the issuance schedule: at first, each block brought 50 new BTC as part of the block rewardGlossaryBlock rewardWhat a miner receives for a valid block: newly created bitcoin (the subsidy) plus the fees of all transactions in the block. The subsidy halves every 210,000 blocks; on 20 April 2024 it fell to 3.125 BTC.On the learning path: Stage 2 · Step 2 – Halving & 21 million →In the glossary →×, and every 210,000 blocks this amount halves (halvingGlossaryHalvingEvery 210,000 blocks – roughly every four years – the number of new bitcoin per block is cut in half. The fourth halving, on 20 April 2024, reduced it from 6.25 to 3.125 BTC.On the learning path: Stage 2 · Step 2 – Halving & 21 million →In the glossary →×). Because only whole satoshisGlossarySatoshi (sats)The smallest unit of Bitcoin: 1 satoshi (‘sat’ for short) equals 0.00000001 BTC, so one bitcoin consists of 100 million sats. The unit is named after Bitcoin’s creator, Satoshi Nakamoto.On the learning path: Stage 1 · Step 4 – Sats & units →In the glossary →× are issued, this adds up to at most 20,999,999.9769 BTC; the last satoshis are expected around 2140.^[1]

The value MAX_MONEY of 21 million BTC in the Bitcoin Core code is not the money supply but a sanity check: no single amount may be larger.^[2]

How much exists already?

Right now, 20,093,887 BTC have been issued, i.e. 95.69% of 21 million; 906,113 BTC are still to come. Fewer are usable, because bitcoin whose keys are lost are out of reach forever.^[1]

Can the limit be changed?

Software can be changed. But every full nodeGlossaryFull nodeA node that checks every block and every transaction itself against all the consensus rules. If you run a full node, you don’t have to trust anyone to know whether a payment is valid.In the glossary →× rejects blocks that create more new bitcoin than allowed. A larger supply would therefore have to be wanted – and installed – by a great many users themselves. Anyone who deviates alone ends up on a chain of their own, with a different currency.

Scarcity alone doesn’t guarantee a price. More in The halving & the 21 million and Digital scarcity.