What is Bitcoin’s programmed maximum supply of coins?

Bitcoin’s programmed maximum supply is 21 million bitcoins.

The protocol limits the eventual number of bitcoins by controlling the block subsidy paid to miners and periodically reducing that subsidy. These reductions are commonly called halvings because the new-coin reward is approximately cut in half at regular block intervals.

Bitcoin’s supply is not issued all at once. New coins enter circulation as miners add valid blocks, and the decreasing subsidy means the final fractions are expected to be issued gradually. The exact approach toward the limit depends on Bitcoin’s consensus rules and rounding behavior.

The 21-million figure describes the protocol’s intended cap, not the number currently in circulation. Some coins may also be permanently inaccessible because private keys have been lost, so the spendable supply can be lower than the total issued amount.