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Satoshi Gazette
Glossary

Halving

The block, every 210,000, at which the block subsidy is cut in half: heights 210,000, 420,000, 630,000 and 840,000 so far, the next at 1,050,000. Fees are not halved.

Mining

Definition dated

also halvening · subsidy halving

Bitcoin's issuance schedule is written in blocks, not years. The subsidy starts at 50 BTC and halves at every multiple of 210,000 blocks: to 25 BTC at block 210,000 in November 2012, 12.5 at 420,000 in July 2016, 6.25 at 630,000 in May 2020 and 3.125 at 840,000 in April 2024. The next halving is at block 1,050,000.

The Gazette dates a halving by its height first. The calendar date of a future halving is an estimate that shifts whenever blocks arrive faster or slower than ten minutes; the height does not shift.

The subsidy is counted in whole satoshis, so the halvings do not go on forever: after the 32nd it is one satoshi, and the 33rd, at block 6,930,000, takes it to zero.

Common misreadings3

  • People say

    The halving happens every four years

    Precisely

    It happens every 210,000 blocks. At ten minutes a block that is about four years, but the date moves with the hashrate.

  • People say

    The halving halves miners' income

    Precisely

    It halves the subsidy. Fees are not halved, so the effect on a miner's reward depends on how much of it fees already pay.

  • People say

    The halving halves the supply

    Precisely

    It halves the rate at which new bitcoin is created. The issued supply keeps growing, more slowly.