The supply cap
Where the cap comes from
It is written into the protocol as an issuance schedule rather than as a stated limit. Every block rewards its miner with newly created coins, and that reward halves every 210 000 blocks, which works out to roughly four years.
The reward started at 50 coins in 2009. It fell to 25, then 12,5, then 6,25, and stood at 3,125 after the halving of April 2024. Each halving cuts new issuance in half, and the sum of that shrinking series converges just below 21 million.
The last fraction of a coin will be mined around the year 2140. After that miners are paid entirely from transaction fees, which is a change the network has yet to live through.
How many are actually available
Fewer than the mined figure suggests, and by a large margin.
Estimates of permanently lost coins run between three and four million: keys thrown away, hard drives discarded, holders who died without passing on a seed phrase, and the roughly 1,1 million attributed to Bitcoin’s creator that have never moved.
Nobody can prove a coin is lost. The chain records only that an address has not transacted, and an address dormant for fifteen years is indistinguishable from one whose owner is simply patient. Estimates are inferences, and they are worth treating as such.
Subtracting the plausible losses leaves something closer to sixteen million coins in genuine circulation.
Why the cap matters
Why the cap is treated as the point
Fixed supply is the property people mean when they compare Bitcoin to gold, and it is the clearest structural difference between it and government-issued money. A central bank can expand fiat supply by decision. Bitcoin issuance follows a schedule that no participant can alter without the agreement of essentially everyone running the network.
Whether scarcity produces value is a separate argument and not one this entry needs to settle. What the cap does reliably is make future supply knowable, which is unusual for any asset.
Dogecoin makes the useful contrast: no cap at all, roughly five billion new coins issued each year, and a network that works perfectly well for payments regardless.
What it means for a merchant
What this means for a merchant
Almost nothing operationally, which is worth saying plainly.
Supply mechanics affect price over long horizons. A business that converts on receipt holds Bitcoin for minutes and is unaffected by anything happening on a fourteen-year timescale.
The one place it surfaces is divisibility. Because the total is small, Bitcoin is denominated in fractions: one coin divides into 100 million satoshis, and ordinary retail payments are usually quoted in those rather than in whole coins.