Bitcoin Halving: What It Is, When the Next One Is, and What It Changes

A Bitcoin halving is the point where the number of new bitcoins paid to miners for each block falls by half. It happens every 210,000 blocks, which is about every four years. The most recent halving was at block 840,000 on 20 April 2024, when the subsidy fell from 6.25 BTC to 3.125 BTC. The next one comes at block 1,050,000 and cuts the subsidy to 1.5625 BTC. At the chain height on 25 October 2026 (block 973,067), that is about 77,000 blocks away, or roughly spring 2028 if blocks keep arriving at their target pace.

How the halving works

It is one line of consensus code

The halving is not a vote or a scheduled announcement. Every Bitcoin Core node calculates the subsidy from the block height. In the function GetBlockSubsidy in validation.cpp:

• the number of halvings so far is the block height divided by nSubsidyHalvingInterval, which is set to 210000 on mainnet;
• the subsidy starts at 50 BTC (50 * COIN) and is shifted right by one bit per halving, so it halves each time;
• the code comment reads: "Subsidy is cut in half every 210,000 blocks which will occur approximately every 4 years."

The miner claims the subsidy in the block's generation transaction. A block that pays itself more than the allowed subsidy plus fees is invalid, and other nodes reject it. That is why the schedule holds without any central party enforcing it.

Why it is "about" four years, not exactly

The halving is set by blocks, not by dates. Bitcoin targets one block every ten minutes, so 210,000 blocks take about 4 years (210,000 × 10 minutes ≈ 1,458 days). When hash rate rises faster than the difficulty adjustment can follow, blocks come slightly faster and the halving arrives early. Between block 840,000 (20 April 2024) and block 973,067 (25 October 2026), the network produced slightly more blocks than the ten-minute target would give. Any calendar date for the next halving is an estimate.

Every halving so far

Dates for the four past halvings are taken from the block timestamps.

The 2024 halving block

Block 840,000 shows that the subsidy is not the miner's only income. Its generation transaction paid a total reward of 40.75 BTC. Of that, 3.125 BTC was subsidy and about 37.63 BTC was transaction fees from 3,050 transactions. That fee level was a one-off spike at the halving block, not a typical day.

What the halving changes

New supply

• Issuance rate: at 3.125 BTC per block and about 144 blocks a day, the network creates about 164,000 new BTC a year. After the 2028 halving that falls to about 82,000 a year (calculated from the subsidy schedule).
• Coins already issued: adding up the subsidy schedule to block 973,067 gives about 20.1 million BTC, roughly 96% of the eventual total. This is an upper bound, because some miners claimed less than the full subsidy.
• The cap is a limit the supply approaches but never reaches: because amounts are whole numbers of satoshis and the subsidy is rounded down at each halving, the maximum is 20,999,999.9769 BTC rather than exactly 21 million, according to the Bitcoin Wiki's supply table.

When issuance ends

Each halving rounds the subsidy down to whole satoshis. After 33 halvings it reaches zero, from block 6,930,000 onward. The Bitcoin Wiki estimates the last satoshi will be mined around 2140 and notes that an exact date cannot be predicted. The Core code also returns zero after 64 halvings, so the bit shift never becomes undefined. That limit is a safeguard; the subsidy already reaches zero long before it.

Miners

Each halving cuts a miner's bitcoin income per block in half overnight, while electricity and hardware costs stay the same. Miners with higher costs become unprofitable first. What happens next depends on the bitcoin price and on fees, neither of which the protocol sets. Over the long run, Bitcoin's security budget has to move from subsidy to fees. Bitcoin.org's FAQ expects that once issuance ends, miners "will probably be supported exclusively by numerous small transaction fees". Whether fees will be enough is an open question, and no primary source settles it.

Price

The halving reduces new supply on a known date. It does not change demand, and the date is public years ahead, so it is not news to the market. There have been four halvings, which is far too few to draw a reliable pattern from, and each one happened in a different economic and regulatory setting. Claims that a halving "makes Bitcoin more valuable" or reliably comes before a rally are speculation, not a property of the protocol.

Common misconceptions

• "The halving happens every 210,000 coins." Wrong: it happens every 210,000 blocks.
• "Fewer miners make Bitcoin less secure straight away." Difficulty adjusts every 2,016 blocks, so block times recover if hash rate drops. Security depends on how much hash power is committed, which the halving can reduce. It does not switch off.
• "Bitcoin ends in 2140." Only the subsidy ends. Blocks, transactions and fees continue.
• "The cap is exactly 21 million." The maximum is slightly lower, as explained above.

Limitations

Supply totals and the 2028 date are calculated from the published subsidy rules and the chain height on 25 October 2026. They are not official forecasts, and the price discussion does not predict anything.