I always thought 21 million $BTC was just a “pretty” number Satoshi picked for marketing 🤭. I went digging through the code, not the legends.
Turns out, it’s more mundane and, at the same time, more interesting.
The limit doesn’t come from a separate decision to “make it 21 million,” but from the protocol’s mathematics: the block reward started at 50 BTC and is cut in half every 210,000 blocks, about once every four years. Add up this progression down to zero, and you get exactly 21 million.
A few details that surprised me:
— the last whole BTC is expected to be mined around 2140 — issuance is spread out over more than a century;
— rewards are calculated in whole satoshis, so the actual final supply will be slightly less than exactly 21,000,000 due to rounding in the final stages;
— the limit was built into the first publicly released code in 2009, not added later — deflation wasn’t something that “evolved”; it was part of the design from the very beginning.
What struck me most: the fixed limit is a deliberate contrast with fiat, where the amount of money issued can be changed by a central bank. Here, the rule is in the code, and changing it would mean creating a different asset.
Have you ever worked out for yourself why it’s exactly 21 million, or have you simply taken that number for granted?👇
$BTC
Turns out, it’s more mundane and, at the same time, more interesting.
The limit doesn’t come from a separate decision to “make it 21 million,” but from the protocol’s mathematics: the block reward started at 50 BTC and is cut in half every 210,000 blocks, about once every four years. Add up this progression down to zero, and you get exactly 21 million.
A few details that surprised me:
— the last whole BTC is expected to be mined around 2140 — issuance is spread out over more than a century;
— rewards are calculated in whole satoshis, so the actual final supply will be slightly less than exactly 21,000,000 due to rounding in the final stages;
— the limit was built into the first publicly released code in 2009, not added later — deflation wasn’t something that “evolved”; it was part of the design from the very beginning.
What struck me most: the fixed limit is a deliberate contrast with fiat, where the amount of money issued can be changed by a central bank. Here, the rule is in the code, and changing it would mean creating a different asset.
Have you ever worked out for yourself why it’s exactly 21 million, or have you simply taken that number for granted?👇
$BTC