The Halving

The halving is a rule written into Bitcoin’s software that cuts the reward for mining a block in half every 210,000 blocks. At roughly 10 minutes per block, that works out to about every four years.

The schedule so far

Year	Block height	Reward per block
2009	0	50 BTC
2012	210,000	25 BTC
2016	420,000	12.5 BTC
2020	630,000	6.25 BTC
2024	840,000	3.125 BTC

The next halving is expected around 2028, at block 1,050,000. Because the timing depends on how fast blocks are found, the exact date can only be estimated.

Why supply stops at 21 million

Each halving period creates half as many new bitcoins as the one before: 10.5 million in the first period, 5.25 million in the second, and so on. Adding up that shrinking series gives a total just under 21 million. The reward will reach effectively zero around the year 2140, after which miners will be paid only by transaction fees.

What it does and doesn’t mean

The halving reduces how many new bitcoins enter circulation. It does not change how many already exist, and it does not guarantee anything about the price. Past halvings have been followed by large price rises, but with only a handful of examples, each in very different market conditions, that history is far too thin to treat as a rule. Treat any claim that “the halving will make the price go up” as speculation.

It also squeezes miners: their reward in bitcoin halves overnight, so less efficient operations can become unprofitable unless the price or fees rise.

Related: How Bitcoin Mining Works