By How Many Bitcoins Are There, and What Happens Next?
Bitcoin's total supply is capped at exactly 21 million coins, a limit written directly into the protocol's code rather than set by any policy that could later change. As of this writing, the network is closing in on 20 million mined, a milestone expected within weeks. Here's how that number is actually reached, and what happens once it is.
Why exactly 21 million
The cap is a direct mathematical consequence of Bitcoin's issuance schedule, not a separately chosen target. Block rewards start at 50 BTC and halve roughly every four years (every 210,000 blocks). Summing that entire geometric sequence out to its limit produces a total just under 21 million, an emergent property of the halving schedule rather than a number Satoshi picked and then built the schedule around.
Where the count actually stands
Roughly 95 percent of all bitcoin that will ever exist has already been mined. The current block reward is 3.125 BTC, following the April 2024 halving, with new coins entering circulation at around 450 BTC per day. The next halving, expected around April 2028, will cut that to 1.5625 BTC per block, slowing new issuance even further.
The math behind the very long tail
Because the reward keeps halving rather than stopping abruptly, the remaining fraction of a percent of Bitcoin's supply gets released extremely slowly. The final new bitcoin isn't expected to be mined until around the year 2140, over a century from now, as the block reward shrinks toward fractions of a single satoshi before eventually rounding down to zero under the protocol's integer math.
What happens to miners after that
Once block rewards fully end, miners are compensated entirely by transaction fees instead of newly issued coins. Whether fee revenue alone will be enough to sustain the same level of network security a century from now is an open question among researchers, though it's also a question with over 100 years of runway and multiple halving cycles left to adjust before it becomes urgent.
The supply isn't the same as the usable supply
The 21 million figure counts every coin ever mined, not every coin anyone can still actually access. Analysts estimate somewhere in the range of 3 to 4 million BTC are permanently lost to misplaced keys, forgotten passwords, and old hardware, on top of the roughly 1.1 million widely believed to belong to Satoshi Nakamoto and never spent. The effectively circulating, reachable supply is meaningfully smaller than the headline number.
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Try the key collider nowWhat it comes down to
Bitcoin's scarcity is an arithmetic outcome of a public, unchanged issuance schedule running since 2009, not a marketing claim. For more on how that schedule connects to where new coins actually come from, see how Bitcoin mining works, or for how a meaningful chunk of the existing supply became permanently unreachable, see the Bitcoin buried in a landfill.