Why is there a limit of 21 million Bitcoins?
Bitcoin's total supply is strictly capped at 21 million coins, making it mathematically scarce by design.
Unlike traditional currencies controlled by central banks, Bitcoin has a hard-coded limit built into its source code. Every four years, a "halving" event cuts the mining reward in half, slowing the creation of new coins. This process continues until the final Bitcoin is mined around 2140. This built-in scarcity prevents inflation and ensures no central authority can devalue the currency by printing more.
Nerd Mode
Bitcoin's supply limit is governed by its source code, specifically the 'GetBlockSubsidy' function. When Satoshi Nakamoto launched the network on January 3, 2009, the initial block reward was 50 BTC. The protocol dictates that this reward halves every 210,000 blocks, which takes approximately four years based on a ten-minute average block interval.The first halving occurred on November 28, 2012, reducing the reward to 25 BTC. Subsequent halvings in 2016 and 2020 further reduced the issuance to 12.5 and 6.25 BTC respectively. Following the April 2024 halving, the reward dropped to 3.125 BTC. This geometric series ensures the total number of Bitcoins will never exceed 20,999,999.9769 units.This deflationary mechanism is central to "Stock-to-Flow" modeling, which compares existing supply to annual production rate. By 2140, miners will no longer receive newly created coins and will instead be compensated solely through transaction fees. This mathematical certainty contrasts sharply with fiat currencies like the US Dollar, where the Federal Reserve can expand the money supply (M2) at its discretion.
Verified Fact
FP-0003604 · Feb 18, 2026