ASIC Mining Glossary
What is the Bitcoin halving?
The halving is the event that cuts the number of new bitcoins paid to miners in half. It happens every 210,000 blocks, roughly every four years, and it is written into Bitcoin's code.
Each block pays the miner who finds it a block reward made of two parts: the block subsidy (newly created bitcoins) and the transaction fees paid by users. The halving only affects the subsidy. It is how Bitcoin limits its total supply to 21 million coins.
Why Bitcoin has halvings
Bitcoin was designed with a fixed maximum supply of 21 million coins. Instead of creating new coins at a constant rate, the protocol releases them on a decreasing schedule: half of all bitcoins were issued in the first four years, a quarter in the next four, and so on. More than 19.8 million bitcoins already exist, so each halving now changes the new supply by a smaller amount, while the effect on miners' revenue stays large.
Transaction fees are the other part of the block reward. They depend on how busy the network is: most of the time they are a small share of miners' revenue, but they can rise sharply during periods of heavy demand. Over the long term, fees are expected to replace the subsidy as miners' main income.
Bitcoin halving history
| Event | Block | Date | Subsidy per block |
|---|---|---|---|
| Launch | 0 | January 2009 | 50 BTC |
| 1st halving | 210,000 | November 28, 2012 | 25 BTC |
| 2nd halving | 420,000 | July 9, 2016 | 12.5 BTC |
| 3rd halving | 630,000 | May 11, 2020 | 6.25 BTC |
| 4th halving | 840,000 | April 20, 2024 | 3.125 BTC |
| 5th halving | 1,050,000 | Expected around spring 2028 | 1.5625 BTC |
The exact date depends on how fast blocks are found. Follow the live estimate on our next Bitcoin halving countdown.
What the halving means for ASIC miners
On the day of the halving, every miner earns half as many new bitcoins for the same hashrate. The hashprice (revenue per unit of hashrate per day) falls accordingly, unless the Bitcoin price or transaction fees rise enough to compensate. Electricity costs, on the other hand, do not change.
Worked example, all else being equal
On September 29, 2026 the hashprice was about $40 per PH/s per day (OMS calculator data). If it fell by half to $20 with no change in Bitcoin price, fees or difficulty, at $0.08 per kWh:
- Antminer S21 XP (270 TH/s, 13.5 J/TH): revenue $5.40 per day against $7.00 of electricity. Break-even would move to about $0.06 per kWh.
- Antminer S21 (151 TH/s, 17.5 J/TH): revenue $3.02 per day against $5.07 of electricity. Break-even would move to about $0.048 per kWh.
This is an illustration, not a forecast. After past halvings the Bitcoin price, transaction fees and network difficulty all moved; no future result is guaranteed.
That is why energy efficiency and the electricity rate matter most around a halving. The least efficient machines are switched off first, the network hashrate can drop for a while, and difficulty adjusts every 2,016 blocks, about every two weeks, which gives part of the revenue back to the miners who stay online.
Halvings on other coins
- Litecoin: halves every 840,000 blocks, also about every four years. The last halving in August 2023 cut the reward from 12.5 to 6.25 LTC; the next one is expected in 2027.
- Dogecoin: has no halving. Each block pays a fixed 10,000 DOGE, which Scrypt miners often mine together with Litecoin through merged mining.
- Bitcoin Cash: follows the same schedule as Bitcoin, with its last halving in April 2024.
How miners prepare
- Compare machines by J/TH, not only by hashrate.
- Secure the lowest possible electricity rate, or hosting with a fixed price per kWh.
- Estimate the payback period with a lower hashprice after the halving, not only with today's figure.
- Plan firmware tuning: underclocking an older machine can keep it profitable longer.
Frequently asked questions
When is the next Bitcoin halving?
At block 1,050,000, expected around spring 2028. The halving countdown updates the estimate from the current block height.
Will my miner stop working after the halving?
No. The machine keeps producing the same hashrate; only the reward per terahash changes. Whether it stays profitable depends on your electricity cost and the market.
What happens when all 21 million bitcoins are mined?
The subsidy reaches zero around the year 2140. Miners will then be paid by transaction fees only.