21 Million

21 million is the maximum number of bitcoin that will ever exist, a limit written into the protocol since its 2009 launch. New coins enter circulation as block subsidies that halve every 210,000 blocks, so issuance approaches the cap asymptotically: about 95 percent of all bitcoin has already been mined, and the final fraction arrives around the year 2140.

Why it matters

The cap is bitcoin's defining monetary promise: no committee, emergency, or majority of miners can issue coin number 21,000,001 while users run software that enforces the rule. Every full node independently verifies that each block creates only the permitted subsidy, so inflating the supply would require convincing the economic majority of users to adopt new rules against their own interest. The credibility of this arrangement is the foundation of every bitcoin valuation thesis. It is also why lost coins matter: bitcoin sent to unspendable addresses or stranded by lost keys shrinks the effective supply below the cap permanently.

In the gold vs bitcoin debate

Gold is scarce; bitcoin is finite. Gold's above-ground stock, over 200,000 tonnes, grows every year, and no one knows how much remains in the earth's crust, the oceans, or asteroids that future technology might reach. Bitcoin's total is a known integer. Whether a fixed cap is superior to slow, predictable growth is genuinely debated among economists, but the 21 million limit is the single clearest difference between the two assets and the anchor of bitcoin's claim to be the scarcest money ever created. The number itself is arbitrary; the fact that it cannot be changed without user consensus is what carries the weight.