Why There Are Only 21 Million Bitcoin

Why are there only 21 million bitcoin? Because the program says so: every new block brings a fixed reward, and that reward halves every 210’000 blocks, roughly every four years. Add up all the rewards and you never get past 21 million. Every node in the world checks this with every block and rejects blocks that create more.

The savings in your bank account lose a little value every year, because new money is created somewhere and you have no say in it. Bitcoin promises the opposite: a supply that is fixed. Sounds good, but how do you know it's true? And what stops someone from changing the rule tomorrow? This article walks you through it step by step. If bitcoin is completely new to you, the beginner's guide What is Bitcoin? starts one step earlier.

How the 21 million come about

New bitcoin are created in only one way: a miner adds a new block to the blockchain and may pay itself a reward for doing so. That happens about once every ten minutes.

The reward follows a simple rule:

1. It starts at 50 bitcoin per block. That was the case from the first block on Jan 3, 2009.
2. Every 210’000 blocks the reward halves. At ten minutes per block, that is almost exactly four years. This moment is called the halving.
3. At some point the reward is smaller than the smallest unit. From then on, no new bitcoin are created.

So each epoch brings half as many new bitcoin as the one before. The first brought 10.5 million, the second 5.25 million, the third 2.625 million. This series gets ever closer to 21 million without ever passing it, just as you never reach a wall if each time you walk only half the remaining distance.

How many bitcoin exist today?

As of Nov 13, 2026, the blockchain stands at block 975’637. Since the halving in April 2024, each block brings 3.125 BTC. That means about 20’111’000 bitcoin exist, 95.8% of all bitcoin there will ever be. About 889’000 are still to come.

A halving comes every 210’000 blocks, so the fifth at block 1’050’000, expected in spring 2028. "Share" means how much of the final supply exists after it.

Half of all bitcoin had already been mined after four years, three quarters after a little over seven. The last 4% are spread over more than a hundred years. What happens at each halving and how the price developed afterwards is a topic of its own: the Bitcoin halving.

Bitcoin's inflation rate

Today about 144 blocks of 3.125 BTC each are created per day, or about 164’000 bitcoin a year. Measured against 20.11 million, that is 0.82% a year. After the 2028 halving the rate falls to about 0.4%, and then halves again every four years.

For comparison: gold grows by about 1.7% a year through new mining (Bitcoin vs. gold compared). And the euro and the franc have no fixed upper limit at all; their supply is decided by central banks and commercial banks. Why that costs purchasing power is shown in Inflation and the loss of purchasing power.

Why exactly 21 million?

The honest answer: the number is not magic. Satoshi Nakamoto wrote to developer Mike Hearn on Apr 12, 2009:

"My choice for the number of coins and distribution schedule was an educated guess. […] I wanted to pick something that would make prices similar to existing currencies, but without knowing the future, that's very hard."

In the same message he explained the logic: if bitcoin stays a niche, each unit is worth little. If it is used for a share of world commerce, there are only 21 million coins for the whole world, and each unit is worth much more.

The two other numbers follow from practical considerations:

• Ten minutes per block leaves enough time for a new block to spread around the world before the next one arrives. The difficulty adjustment keeps this pace steady, no matter how many miners take part.
• 210’000 blocks at ten minutes are about four years. That spreads the new coins over generations instead of only to the first users.

Had Satoshi chosen 21 billion, each unit would simply be a thousand times smaller. What counts for value is not the number but that it applies to everyone equally and forever.

Who protects the cap

The rule is written in the software every node runs. A node is a computer that keeps a full copy of the blockchain and checks every new block. If a miner pays itself even one satoshi more than allowed, its block is invalid. The nodes don't pass it on, and the miner has burned its electricity for nothing.

That means miners write the blocks, but they don't set the rules. The nodes set the rules, and there are tens of thousands of them, run by individuals, companies and exchanges. Every exchange that checks deposits does so with its own node. You can run your own node with little effort, as Running your own Bitcoin node shows. Then you check the 21 million yourself instead of trusting someone.

Nearly broken twice, repaired twice

There have been bugs in the code, and both show how seriously the network takes the cap:

• Aug 15, 2010: A calculation error allowed a transaction that created more than 184 billion bitcoin out of thin air (block 74’638). Within a few hours a corrected version was out, and the nodes switched to a chain without that block. The false coins do not exist today.
• September 2018: Developers found a bug through which a miner could have spent coins twice and so created new ones (CVE-2018-17144). It was fixed and disclosed before anyone exploited it.

Anyone can check today that the supply is right: on command, a node adds up all existing coins (gettxoutsetinfo).

Can the cap be changed?

Technically yes: someone writes a new software version with more bitcoin. In practice, though, every node, every exchange and every user would have to install that version voluntarily. Anyone who doesn't stays on the old chain, and the new one is a separate, different coin.

Why would anyone agree? Anyone who holds bitcoin would dilute their own share. That is exactly why the cap is considered the most stable rule in the system. Even over much smaller questions, such as the block size in 2017, a minority split off, and the original chain kept the name, the users and the far higher price. How changes to Bitcoin come about at all is explained in Soft forks, Taproot and future upgrades.

There are fewer than 21 million

The real amount that can ever be moved is well below that:

• The genesis block: The 50 bitcoin from the very first block cannot be spent because of a quirk in the code.
• Lost keys: If you lose your seed phrase, you lose the coins forever. In 2020 Chainalysis estimated that about 3.7 million bitcoin are probably lost, including about one million from the early days that are attributed to Satoshi and have never moved.
• Not fully claimed: Some early miners paid themselves less than they were allowed to. What was not claimed is never created.

Nobody knows exactly how many bitcoin are really lost. The only certainty: every loss makes the rest scarcer. To keep yours from being among them, read the guide How to store Bitcoin safely.

What 21 million mean for you

About 8.2 billion people live on Earth. Even if every unit were shared out equally, each person would get only 0.00256 bitcoin, or 256’000 sats.

You don't need a whole bitcoin for this. Each bitcoin has 100 million sats, so there are 2.1 quadrillion sats in total. Work it out with your own amount:

Whether to aim for a whole bitcoin in the long run or to set an intermediate goal in sats is covered in Becoming a wholecoiner.

Scarcity is no price promise

A fixed supply says nothing about demand. Since 2011 bitcoin has fallen four times by 77 to 93%, even though the supply was fixed the whole time. The long-term trend and where the price stands against it today are shown in the Power Law analysis. On Nov 13, 2026, the price was about 0.63 times the trend, just above the floor. How we calculate that is in the methodology.

What happens when all 21 million have been mined?

Around the year 2140, the last satoshi comes out of the block reward. The network keeps running as before. Instead of new coins, miners then receive only the fees users pay for their transactions.

Whether fees will then be enough to keep the network secure is an open question that developers and economists seriously debate. Until then, though, the reward shrinks in small steps over more than a hundred years, and the share of fees in miners' income grows gradually. How fees come about is shown in Understanding transaction fees and the mempool.