The next halving happens at block 1,050,000 — roughly four years after the April 2024 event. The exact date depends on actual block-production speed; this page estimates the ETA from current tip height assuming 10-minute average blocks.
The block reward (newly minted BTC paid to whichever miner solves the block) is cut in half. After the 4th halving in April 2024, the reward dropped from 6.25 BTC to 3.125 BTC. The 5th halving will drop it to 1.5625 BTC.
Halvings are how Bitcoin enforces its capped supply. Every 210,000 blocks (~4 years) the issuance rate halves; total ever-mintable supply converges to 21 million BTC by approximately the year 2140.
The countdown assumes 10 minutes per block — Bitcoin's long-term average. In practice blocks vary; weeks of fast or slow blocks can shift the actual date by several days. The block-height display, by contrast, is exact.