Key Takeaways
Quick answer
A halving is the scheduled moment when the reward Bitcoin pays for each new block drops by half. It happens every 210,000 blocks, roughly every four years. The reward started at 50 BTC, and repeated halvings are why total supply ends just under 21 million.
- Every 210,000 blocks the Bitcoin block reward is cut in half, starting from 50 BTC.
- Adding up every era gives just under 21 million bitcoin in total.
- No official source shows halvings push prices up, and regulators document sharp falls.
What exactly gets halved?
New bitcoin enter circulation only one way: as a subsidy paid to whoever adds the next block through proof of work. Bitcoin Core’s source code sets that subsidy at 50 BTC at the start and halves it every 210,000 blocks on the main network.
Why about four years? The network targets one block every 10 minutes. Illustrative arithmetic: 210,000 blocks × 10 minutes gives 2,100,000 minutes; divided by 1,440 minutes a day, that is roughly 1,458 days, just under four years. Real block times vary, so the dates drift.
How does the schedule add up to almost 21 million?
| Era | Reward per block | New BTC in era |
|---|---|---|
| 1 | 50 | 10,500,000 |
| 2 | 25 | 5,250,000 |
| 3 | 12.5 | 2,625,000 |
| 4 | 6.25 | 1,312,500 |
Each row is 210,000 × the reward. Half of all bitcoin ever issued came from the first era alone. Summing every era in satoshi, the smallest unit, gives 20,999,999.9769 BTC, slightly under 21 million, because the code rounds the subsidy down until it reaches zero.
Does a halving make the price go up?
We found no official source showing that halvings cause price rises, and claims that a fixed supply must lift the price are not established. What regulators do document is how far prices can fall. Figures from the UK Financial Conduct Authority (FCA) put Bitcoin at £93,947 at its 6 October 2025 peak and £65,350 on 1 December 2025, down 30.44% in under two months. The wider picture is in our guide to crypto risks.
Frequently asked questions
How often does the Bitcoin halving happen?
Every 210,000 blocks. At the 10-minute target that is close to four years, but the exact date depends on how fast blocks are actually found.
Will exactly 21 million bitcoin ever exist?
No. The source code itself says the actual supply is less than 21,000,000 BTC. The schedule sums to about 0.0231 BTC short of that figure. See what Bitcoin is for the wider picture.
What happens when the rewards run out?
The code forces the subsidy to zero after 64 halvings, and by its rounding it reaches zero much earlier. From then on, the Bitcoin whitepaper says the incentive can shift entirely to transaction fees.
Article Sources
5 sources
Blockhorizon checks every figure, date and quotation against primary sources: regulators, statistics bodies and original technical documents. Read our editorial policy.
- Bitcoin Core source code — validation.cpp, GetBlockSubsidy() — github.com (accessed 2026-10-02)
- Bitcoin Core source code — kernel/chainparams.cpp (main network parameters) — github.com (accessed 2026-10-02)
- Bitcoin Core source code — consensus/amount.h (MAX_MONEY) — github.com (accessed 2026-10-02)
- Satoshi Nakamoto, Bitcoin: A Peer-to-Peer Electronic Cash System (whitepaper, 2008) — bitcoin.org (accessed 2026-10-02)
- UK Financial Conduct Authority, Crypto: the basics (updated Jan 2026) — fca.org.uk (accessed 2026-10-02)