The Halvings | Bitcoin stories

Every 210,000 blocks, the block subsidy halves. It's the most important line of code in Bitcoin: the function that turns a deflationary supply schedule from a cypherpunk dream into a deterministic asymptote. Four halvings have happened so far. You can see each one happen in the coinbase transactions on either side of the boundary.

The math is simple: subsidy starts at 50 BTC, halves at heights 210,000, 420,000, 630,000, 840,000, and so on, until it eventually reaches zero around the year 2140. After that, miners earn only fees.

Halving 1, height 210,000 (November 28, 2012)

Block 209,999 still paid the original 50 BTC subsidy. The very next block, 210,000, paid only 25 BTC.

Last 50-BTC block:

Open in playground → subsidy: 5,000,000,000 sat

First 25-BTC block:

Open in playground → subsidy: 2,500,000,000 sat

Subsidies are reported in satoshis (1 BTC = 100,000,000 sat). Block 209,999's subsidy reads 5000000000, exactly 50 BTC. Block 210,000's reads 2500000000, exactly 25 BTC. Determinism in action.

Halving 2, height 420,000 (July 9, 2016)

Subsidy drops from 25 BTC to 12.5 BTC.

Open in playground → last 25-BTC block

Open in playground → first 12.5-BTC block

Halving 3, height 630,000 (May 11, 2020)

Subsidy drops from 12.5 BTC to 6.25 BTC. This is the halving that happened during the COVID-era money-printing acceleration, and the contrast got noticed.

Open in playground → last 12.5-BTC block

Open in playground → first 6.25-BTC block

Halving 4, height 840,000 (April 19, 2024)

Subsidy drops from 6.25 BTC to 3.125 BTC. Block 840,000 itself, mined by the ViaBTC pool, was sold at auction by its operator for 33.7 BTC, a curiosity in its own right.

Open in playground → last 6.25-BTC block

Open in playground → first 3.125-BTC block

Chart it

Same data, plotted. Click Load chart to fetch getblockstats at each post-halving block height and render the subsidy curve. (8 RPC calls, ~2 seconds against our node.)

Block subsidy at each post-halving block

The math

Sum of all subsidies (in BTC):

50    BTC × 210,000 blocks = 10,500,000 BTC  (era 1, 2009-2012)
25    BTC × 210,000 blocks =  5,250,000 BTC  (era 2, 2012-2016)
12.5  BTC × 210,000 blocks =  2,625,000 BTC  (era 3, 2016-2020)
6.25  BTC × 210,000 blocks =  1,312,500 BTC  (era 4, 2020-2024)
3.125 BTC × 210,000 blocks =    656,250 BTC  (era 5, 2024-2028)
                              ─────────────
                              20,343,750 BTC  (so far, after 5 eras)

Continue the geometric series and it converges on 21,000,000 BTC. We'll never quite hit it, the last fractional satoshis get rounded out by integer math around the year 2140, but the limit is structural. There's no governance process to change it. There's no committee that could vote to add more. The function is the function.

What's next

Halving 5 will land at height 1,050,000, around April 2028, dropping subsidy to 1.5625 BTC. After that, 0.78125 BTC, then 0.390625 BTC, and so on for 32 more eras until subsidy rounds to zero.

By that point, Bitcoin's miners will be paid entirely by transaction fees. Whether that fee market is strong enough to secure the network is one of the open questions in monetary cryptography, and the entire point of the asymptotic schedule: the answer becomes empirically observable, halving by halving.

You can see today's block subsidy with one query:

Open in playground → current height, then divide by 210000 to find subsidy era