The halving

Bitcoin's built-in clock

Roughly every four years the rate at which new bitcoin are created is cut in half. It's the rule that makes the supply predictable and slowly leads toward the cap of 21 million. Here's the countdown, how blocks and time fit together, the history and why it matters.

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What is a halving?

Every time a new batch of transactions (a block) is added to the blockchain, new bitcoin are created as a reward to whoever secures the network. Every 210,000 blocks, roughly every four years, that reward is halved.

The result is a supply that grows ever more slowly and whose rate is known in advance, all the way to the last bitcoin around the year 2140. No one can change it after the fact.

Read: What makes Bitcoin sound money?

Blocks & time

The halving is measured in blocks, not calendar days. Bitcoin is built so that a new block should be found on average every 10 minutes, but individual blocks can take both shorter and longer.

Target time per block

≈ 10 min

on average, per the protocol

Blocks per halving

210,000

≈ 4 years at target time

Difficulty adjustment

every 2,016 blocks

≈ every 14 days

Blocks per day

≈ 144

at 10 min/block

Why don't we know exactly when the halving happens?

Blocks don't arrive exactly every 10 minutes. Sometimes it's faster, sometimes slower — that's normal.
The network adjusts the difficulty roughly every 14 days so the average time stays near the target, even as computing power (hash rate) changes.
Hash rate can rise or fall quickly as new miners start or shut down. That's why the halving date is an estimate based on the current pace, not an exact time.

Supply in the current epoch

Since the halving in April 2024 the block reward is 3.1250 BTC. The next halving lowers it to 1.5625 BTC.

Block reward now

3.1250 BTC

halved at the next epoch

New supply per day

≈ 450 BTC

at ~144 blocks/day

Share issued

95.5%

20,050,865 of 21,000,000 BTC

Left to mine

949,135 BTC

until around the year 2140

All halvings

From 50 BTC per block at the start to ever less with each epoch.

Halving	Block	Date	Block reward	Status
Start (genesis)	0	2009-01-03	50 BTC	Occurred
#1	210,000	2012-11-28	25 BTC	Occurred
#2	420,000	2016-07-09	12.5 BTC	Occurred
#3	630,000

Why the halving matters

Ordinary money can be printed in unlimited amounts. Bitcoin goes the other way: the inflow of new coins shrinks on a schedule no one can shift. That makes the scarcity credible — you can work out exactly how many bitcoin exist at a given moment.

The halving, then, isn't an event to time, but an illustration of a principle: predictable, scarce money. That's the principle I think is worth understanding.

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The countdown is fetched live from the blockchain; the estimated date is an approximation based on ~10 minutes per block. This is not financial advice.