Bitcoin Halving: What It Is and How It Works

How the halving works

Every new Bitcoin block pays the miner who found it a block reward made of two parts:

1. the block subsidy, newly created bitcoin; and
2. the transaction fees paid by users whose transactions are in the block.

The halving only affects the subsidy. Bitcoin's rules set it at 50 BTC in the first block and divide it by two every 210,000 blocks. In the reference software, Bitcoin Core, this is a single constant, `nSubsidyHalvingInterval = 210000`, and every node enforces it: a block that pays itself more than the allowed subsidy is rejected by the network.

Because Bitcoin's difficulty adjustment keeps blocks coming roughly every 10 minutes, 210,000 blocks take about four years. The halving therefore has no calendar date. It happens at a block height, and the date is only known in advance as an estimate.

No vote is needed and no one can "trigger" or delay it. Changing the schedule would require nearly all of the network to adopt different software, which would effectively be a different coin (a hard fork).

Every Bitcoin halving so far

The fourth halving block was mined late on April 19, 2024 in US time zones, which is why some sources give that date. The date of the fifth halving depends on how fast blocks arrive between now and then.

Why the halving caps Bitcoin's supply

The halvings form a geometric series: 210,000 × (50 + 25 + 12.5 + …). The sum approaches, but never quite reaches, 21 million BTC. After about 32 halvings the subsidy falls below one satoshi (0.00000001 BTC), the smallest unit Bitcoin can express, and becomes zero. That point is commonly estimated to arrive around the year 2140.

In practice most bitcoin has already been issued: half of all coins were created before the first halving, and each four-year epoch adds half as many as the one before. This predictable, declining issuance is what people mean when they call Bitcoin's monetary policy fixed or "disinflationary". Its circulating supply can be checked at any time from the blockchain itself.

Daily new supply: about 144 blocks are mined per day. At a 6.25 BTC reward that meant roughly 900 new BTC a day; after the 20 April 2024 halving cut the reward to 3.125 BTC, it fell to roughly 450 BTC a day. Measured against the roughly 19.7 million BTC already mined by the April 2024 halving (840,000 blocks), annual new issuance is below 1%.

Bitcoin's fixed, known issuance schedule is why it is often compared with gold, and why the "digital gold" label stuck. The stock-to-flow ratio, the existing stock divided by annual new production, is a common scarcity measure and doubles for Bitcoin at each halving. Models that turn that ratio into a price forecast are disputed, and past post-halving price moves happened under very different macro conditions, so they are not a guide to the future. The event is sometimes nicknamed the "halvening".

What the halving means for miners and the network

Overnight, a halving cuts the subsidy part of miners' revenue in half, while their electricity and hardware costs stay the same. Miners with expensive power or older ASIC machines can become unprofitable and switch off, so the network's hash rate may dip before difficulty adjusts and the remaining miners earn more per unit of work.

Over the long run, the subsidy shrinks towards zero, and transaction fees have to carry more of the cost of securing the network. How large fees will be in future is one of the open questions in Bitcoin's design.

Markets often discuss halvings as price events, because new supply falls. Past halvings have coincided with very different market conditions, and many other factors drive price; the halving itself changes only the issuance rate. This page does not predict prices.

Miners with high electricity costs or older machines can become unprofitable and switch off after a halving, which temporarily lowers the network's hash rate. Bitcoin's difficulty adjustment, every 2,016 blocks (roughly two weeks), then resets mining difficulty to the recent block rate, so blocks keep arriving about every 10 minutes and the remaining miners face less competition.

Halvings on other blockchains

Several proof-of-work coins that copied Bitcoin's model also have halvings. Litecoin, for example, halves its subsidy every 840,000 blocks, which at its faster block time is also roughly every four years. Bitcoin Cash kept Bitcoin's schedule after it forked away from Bitcoin. Proof-of-stake networks such as Ethereum do not have halvings; their issuance depends on the amount staked and on protocol rules.