What is a block halving?

Block halving is a mechanism that reduces the rate at which new cryptocurrency units are created. In the case of Bitcoin, it refers to the periodic halving of block rewards earned by miners.

Halvings are central to many cryptocurrency models because they help regulate supply. This controlled issuance stands in sharp contrast to traditional fiat currencies, which can be printed in unlimited amounts.

Bitcoin halvings

As of May 2025, there have been three Bitcoin halving events:

• 1st halving: November 28, 2012 – Block reward reduced from 50 to 25 BTC. Price at the time: ~$12.
• 2nd halving: July 9, 2016 – Block reward reduced from 25 to 12.5 BTC. Price at the time: ~$650.
• 3rd halving: May 11, 2020 – Block reward reduced from 12.5 to 6.25 BTC. Price at the time: ~$8,500.
• 4th halving: April 20, 2024 – Block reward reduced from 6.25 to 3.125 BTC. Price at the time: ~$63,000.

Halvings occur approximately every 210,000 blocks, roughly every four years. In total, there will be 64 Bitcoin halving events until the maximum supply of 21 million BTC has been mined.

This halving mechanism is a core part of Bitcoin‘s code and monetary policy. You can explore its technical implementation on the official Bitcoin Core GitHub page.