What Is a Bitcoin Halving? The Four-Year Cycle Explained
A bitcoin halving cuts the rate of new supply in half roughly every four years. Here is what it is, why it is written into the protocol, and what it means for scarcity.
A bitcoin halving is a scheduled event, written into the protocol, that cuts the number of new bitcoin created in each block in half. It happens every 210,000 blocks — roughly every four years — and it is the mechanism that enforces bitcoin's fixed supply of 21 million coins.
There is no committee that decides when a halving happens. There is no vote. It is arithmetic, executed by every node on the network, and it has run on schedule since the first one in 2012.
How the Schedule Works
When Bitcoin launched in January 2009, each new block created 50 bitcoin. This reward — the block subsidy — is how new coins enter circulation and how miners are paid for securing the network. Every 210,000 blocks, that subsidy halves.
- 2009: 50 BTC per block
- 2012: 25 BTC per block
- 2016: 12.5 BTC per block
- 2020: 6.25 BTC per block
- 2024: 3.125 BTC per block
- 2028 (approximately): 1.5625 BTC per block
The halvings continue until roughly the year 2140, when the subsidy rounds down to zero and no new bitcoin are ever created again. From that point, miners are paid entirely by transaction fees.
Why This Matters: Stock-to-Flow
The halving is not a marketing event. It is a monetary property. Each halving doubles bitcoin's stock-to-flow ratio — the amount of existing supply divided by the amount of new supply produced each year. A higher ratio means a harder asset, one that is more difficult to inflate.
Gold has held its monetary role for millennia partly because its stock-to-flow ratio is high: the above-ground stock is large and annual mining adds only a small fraction. After the 2024 halving, bitcoin's stock-to-flow ratio surpassed gold's. Unlike gold, bitcoin's ratio is known in advance and cannot be pushed higher by a new discovery or a better mining technique.
Compare the stock-to-flow ratios yourself →
What the Halving Does Not Guarantee
Halvings are often discussed alongside price. It is true that each past halving has been followed, eventually, by a higher price. It is not true that the halving causes this on a schedule you can trade. The supply change is known years in advance, which means rational markets should already reflect it.
The honest way to think about the halving is structural, not speculative. It is the moment the issuance of the hardest money ever created gets harder still — automatically, predictably, and without anyone's permission. That is the point.
The reason a fixed supply matters is not that it makes the number go up. It is that no one can make more of it when it suits them to.
Written by
The Bitcoin Transition
The Bitcoin Transition is an educational project of the Bitcoin Education Foundation. We publish from first principles, in the voice of the protocol itself: direct, technically precise, and free from fiat-denominated framing.
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