Definition
Halving is the scheduled event, written into Bitcoin’s protocol, where the block subsidy paid to miners is cut in half. It happens roughly every four years and is the mechanism that enforces Bitcoin’s fixed supply of 21 million coins.
Also known as: the halvening.
How the halving works
Every time a miner solves a block, the protocol lets that miner mint a fixed number of new bitcoin in the coinbase transaction. That newly minted amount is the block subsidy, and it is the larger half of the total block reward (subsidy plus transaction fees). The halving cuts the subsidy in two at a precise interval: every 210,000 blocks.
Because Bitcoin targets one block roughly every ten minutes, 210,000 blocks works out to approximately four years. The subsidy started at 50 BTC in 2009, fell to 25, then 12.5, then 6.25, and after the April 2024 halving it sits at 3.125 BTC per block. The schedule continues until the subsidy rounds down to zero somewhere around the year 2140, after which miners are paid entirely in fees.
Why the halving matters to a miner
The halving is the single largest force acting on mining profitability. Overnight, the same machine doing the same hashrate earns half the bitcoin per block it used to. Network hashrate does not reset, so the revenue you collect per terahash, your sats per terahash, drops sharply unless price climbs to compensate.
This is why the halving is the moment older or thirsty hardware tends to switch off. A unit running at poor efficiency (J/TH) may have cleared its break-even electricity cost comfortably one day and be underwater the next. The lower the subsidy goes, the more the survivors are the rigs with the best efficiency and the cheapest power.
Practical response on home and ASIC rigs
For a home miner, the halving is a forcing function to revisit how your machine is tuned. After a subsidy cut, squeezing more useful work out of every joule matters more than raw output. Many operators turn to undervolting and modest underclocking to push J/TH down, often through a custom firmware tuning stack that calculates per-domain voltage at runtime rather than relying on fixed factory settings. Whether a given rig stays profitable then comes down to your electricity cost and what you do with the heat it produces.
The halving also reshapes the case for solo mining and lottery-style setups. When the subsidy was higher, a small open-source device finding a block was already a long shot; the prize is now smaller in coin terms even as the odds stay astronomical. Yet sovereign Bitcoiners keep pointing hashrate at the network anyway, because every independent miner is one more layer decentralized. If you are sizing or re-tuning a fleet around the new economics, the model-by-model figures in the miner catalog and the trade-offs covered in our firmware comparison are the practical starting points.
Halving and the difficulty backdrop
The halving is often confused with Bitcoin’s other periodic event, the difficulty adjustment, but they are separate. The difficulty adjustment retargets every 2,016 blocks to keep the average block time near ten minutes; it responds to how much hashrate is online. The halving is a fixed monetary event that does not care about hashrate at all. Together they shape your earnings: difficulty governs how much of the reward you can expect to win for your share of the network, while the halving governs how large that reward is in the first place.
Related terms: Block Subsidy, Block Reward, Coinbase Transaction, Difficulty Adjustment, Mining Profitability, Sats Per Terahash
In Simple Terms
The event that cuts Bitcoin's block reward in half every four years, enforcing digital scarcity.
Halving is the scheduled event, written into Bitcoin's protocol, where the block subsidy paid to miners is cut in half. It happens roughly every four years and is the mechanism that enforces Bitcoin's fixed supply of 21 million coins.
Also known as: the halvening.
How the halving works
Every time a miner solves a block, the protocol lets that miner mint a fixed number of new bitcoin in the coinbase transaction. That newly minted amount is the block subsidy, and it is the larger half of the total block reward (subsidy plus transaction fees). The halving cuts the subsidy in two at a precise interval: every 210,000 blocks.
Because Bitcoin targets one block roughly every ten minutes, 210,000 blocks works out to approximately four years. The subsidy started at 50 BTC in 2009, fell to 25, then 12.5, then 6.25, and after the April 2024 halving it sits at 3.125 BTC per block. The schedule continues until the subsidy rounds down to zero somewhere around the year 2140, after which miners are paid entirely in fees.
Why the halving matters to a miner
The halving is the single largest force acting on mining profitability. Overnight, the same machine doing the same hashrate earns half the bitcoin per block it used to. Network hashrate does not reset, so the revenue you collect per terahash, your sats per terahash, drops sharply unless price climbs to compensate.
This is why the halving is the moment older or thirsty hardware tends to switch off. A unit running at poor efficiency (J/TH) may have cleared its break-even electricity cost comfortably one day and be underwater the next. The lower the subsidy goes, the more the survivors are the rigs with the best efficiency and the cheapest power.
Practical response on home and ASIC rigs
For a home miner, the halving is a forcing function to revisit how your machine is tuned. After a subsidy cut, squeezing more useful work out of every joule matters more than raw output. Many operators turn to undervolting and modest underclocking to push J/TH down, often through a custom firmware tuning stack that calculates per-domain voltage at runtime rather than relying on fixed factory settings. Whether a given rig stays profitable then comes down to your electricity cost and what you do with the heat it produces.
The halving also reshapes the case for solo mining and lottery-style setups. When the subsidy was higher, a small open-source device finding a block was already a long shot; the prize is now smaller in coin terms even as the odds stay astronomical. Yet sovereign Bitcoiners keep pointing hashrate at the network anyway, because every independent miner is one more layer decentralized. If you are sizing or re-tuning a fleet around the new economics, the model-by-model figures in the miner catalog and the trade-offs covered in our firmware comparison are the practical starting points.
Halving and the difficulty backdrop
The halving is often confused with Bitcoin's other periodic event, the difficulty adjustment, but they are separate. The difficulty adjustment retargets every 2,016 blocks to keep the average block time near ten minutes; it responds to how much hashrate is online. The halving is a fixed monetary event that does not care about hashrate at all. Together they shape your earnings: difficulty governs how much of the reward you can expect to win for your share of the network, while the halving governs how large that reward is in the first place.
Related terms: Block Subsidy, Block Reward, Coinbase Transaction, Difficulty Adjustment, Mining Profitability, Sats Per Terahash