The halving & the 21 million
Why there will never be more than 21 million bitcoin: the issuance schedule, every halving by block height, MAX_MONEY in the code and the 2010 overflow bug.
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In short~36 sec
- 01New bitcoin are created only as a block reward. It started at 50 BTC in 2009 and halves every 210,000 blocks, roughly every four years.
- 02So far there have been four halvings (2012, 2016, 2020, 2024). The fifth follows at block 1,050,000, probably in spring 2028.
- 03More than 95% of all bitcoin have already been issued. Because of rounding, at most 20,999,999.9769 BTC will exist; the last satoshi arrives around 2140.
- 04The limit is enforced not by a company but by every node. The 2010 overflow bug showed this.
- 05Whether halvings move the price is disputed. Four events are no basis for a forecast.
Good to read firstSats & unitsMoney, inflation & trust
‘There will never be more than 21 million bitcoin.’ You hear that sentence a lot. We’ll show you where this limit is set, how the halving works and who enforces the rule.
The issuance schedule
New bitcoin are created in only one way: as a reward for the miner who finds a block. The whitepaper envisages that, once a predetermined number of coins is in circulation, transaction fees alone remain as the incentive.[1] The numbers are in the program code:
- The block rewardGlossaryBlock rewardWhat a miner receives for a valid block: newly created bitcoin (the subsidy) plus the fees of all transactions in the block. The subsidy halves every 210,000 blocks; on 20 April 2024 it fell to 3.125 BTC.In the glossary → (more precisely: the subsidy) started at 50 BTC per block.[2]
- It halves every 210,000 blocks.[3] At around ten minutes per block, that is roughly every four years.[2]
This event is called the halvingGlossaryHalvingEvery 210,000 blocks – roughly every four years – the number of new bitcoin per block is cut in half. The fourth halving, on 20 April 2024, reduced it from 6.25 to 3.125 BTC.In the glossary →. It is tied to the block height, not to a date. Nobody has to decide on it: every node works out from a block’s height how much reward is allowed.
All halvings at a glance
| Event | Block | Date (UTC) | Reward from then on | Issued by then |
|---|---|---|---|---|
| Launch | 0 | 3 January 2009 | 50 BTC | – |
| 1st halving | 210,000 | 28 November 2012 | 25 BTC | 10.5 million BTC (50%) |
| 2nd halving | 420,000 | 9 July 2016 | 12.5 BTC | 15.75 million BTC (75%) |
| 3rd halving | 630,000 | 11 May 2020 | 6.25 BTC | 18.375 million BTC (87.5%) |
| 4th halving | 840,000 | 20 April 2024 | 3.125 BTC | 19.6875 million BTC (93.75%) |
| 5th halving | 1,050,000 | expected 2028 | 1.5625 BTC | 20.34 million BTC (96.9%) |
| 6th halving | 1,260,000 | expected 2032 | 0.78125 BTC | 20.67 million BTC (98.4%) |
The dates of past halvings come from the block timestamps.[7] Amounts and estimates are our own calculations from the consensus rules.[2],[3]
Where we stand today
20,093,853 BTC
95.69% issued · 906,147 BTC still to be mined
Now: 3.125 BTC per block. Next halving at block 1,050,000, ≈ April 2028 – 79,968 blocks to go.
As of 05/10/2026 · Block height 970,032
Each square stands for 100,000 BTC, the colour shows the halving epoch, and grey squares have not been issued yet. We calculate the figures continuously from the current block height and the issuance rule.[8],[2],[3] The date of the next halving is an estimate based on the average block pace.[9]
Issuance is spread very unevenly over time: half of all bitcoin had been issued by the end of 2012, and by our calculation around 99% will have been issued by about 2035. Between the 2024 and 2028 halvings, around 450 BTC are created per day (144 blocks × 3.125 BTC), so the supply grows by around 0.8% a year, and from 2028 by around 0.4%.
Why ‘21 million’ – and why it’s at most 20,999,999.9769
The number 21 million does not appear in the whitepaper. It follows from the halving rule:
210,000 blocks × 50 BTC = 10.5 million BTC in the first epoch. Each further epoch brings half of the previous one: 10.5 + 5.25 + 2.625 + … This series approaches 21 million but never reaches it.
Show values as a table
| Event | Block | Date | Reward from then | Issued by then |
|---|---|---|---|---|
| Start | 0 | 03/01/2009 | 50 BTC | – |
| 1st halving | 210,000 | 28/11/2012 | 25 BTC | 10,500,000 BTC (50%) |
| 2nd halving | 420,000 | 09/07/2016 | 12.5 BTC | 15,750,000 BTC (75%) |
| 3rd halving | 630,000 | 11/05/2020 | 6.25 BTC | 18,375,000 BTC (87.5%) |
| 4th halving | 840,000 | 20/04/2024 | 3.125 BTC | 19,687,500 BTC (93.75%) |
| 5th halving | 1,050,000 | approx. April 2028 | 1.5625 BTC | 20,343,750 BTC (96.88%) |
| 6th halving | 1,260,000 | approx. April 2032 | 0.78125 BTC | 20,671,875 BTC (98.44%) |
| 7th halving | 1,470,000 | approx. April 2036 | 0.390625 BTC | 20,835,937.5 BTC (99.22%) |
| 8th halving | 1,680,000 | approx. April 2040 | 0.1953125 BTC | 20,917,968.75 BTC (99.61%) |
| 9th halving | 1,890,000 | approx. April 2044 | 0.09765625 BTC | 20,958,984.375 BTC (99.8%) |
| 33rd halving (reward 0) | 6,930,000 | approx. 2140 | 0 BTC | 20,999,999.9769 BTC (100%) |
Own calculation from the consensus rules (Bitcoin Core). Future dates: block height × 10 minutes, as of 05/10/2026 (Block 970,032).
The final supply stays just below 21 million because of rounding: internally, Bitcoin counts only in whole satoshisGlossarySatoshi (sats)The smallest unit of Bitcoin: 1 satoshi (‘sat’ for short) equals 0.00000001 BTC, so one bitcoin consists of 100 million sats. The unit is named after Bitcoin’s creator, Satoshi Nakamoto.On the learning path: Stage 1 · Step 4 – Sats & units →In the glossary → (0.00000001 BTC),[4] and when halving, the code cuts off the decimal places.[2] From the tenth halving (block 2,100,000, expected around 2048), a tiny remainder is lost each time. The final supply is therefore at most 20,999,999.9769 BTC.[5] From block 6,930,000 the reward is zero – at ten minutes per block, around 2140.[2],[5]
MAX_MONEY: the safety line in the code
The source code of Bitcoin CoreGlossaryBitcoin CoreThe most widely used software for Bitcoin nodes, a direct descendant of Satoshi Nakamoto’s first program. It is open source, verifies all blocks and transactions itself and includes a wallet.In the glossary → contains the constant MAX_MONEY, set to 21,000,000 BTC. It is often taken to be ‘the’ limit, but according to the comment in the code it is not the total supply. It is a sanity check: no amount may be larger.[4] The actual limit follows from the halving rule. 2010 showed why the safety line is needed anyway.
The 2010 overflow bug
On 15 August 2010, it was discovered that block 74,638 contained a transaction that had created 184,467,440,737 BTC. Two addresses received around 92.2 billion each.[6] The cause was a programming error: the software checked the sum of the outputs, but with such huge amounts the calculation overflowed – like an old odometer that goes back to 0 after 99,999.[6]
- Within five hours of the discovery, a corrected version was released that rejects such transactions, as well as any output of more than 21 million BTC. This tightened the rules, making it a soft forkGlossarySoft forkA change to the consensus rules that only tightens them. Blocks that follow the new rules remain valid for old nodes – so Bitcoin can be developed further without a chain split, as with SegWit and Taproot.In the glossary →.[6]
- Nodes running the new software ignored the faulty block, and miners kept building on the corrected chain.
- At block 74,691 the corrected chain overtook the faulty one. On the valid chain, the 184 billion BTC do not exist.[6]
The lesson: the limit holds because independent nodes check it, not because a company promises it.
Can the limit be changed?
Software can be changed. But a higher cap would make blocks valid that are invalid today – a hard forkGlossaryHard forkA change to the consensus rules that allows previously invalid blocks. Old nodes reject such blocks; if not everyone goes along, two permanently separate chains emerge – and with them a new, separate currency.In the glossary →. Every node running the old software rejects such blocks. Two chains would emerge, and the one with more bitcoin would be a different currency. The change could only be pushed through if practically all users adopted it voluntarily.
How hard even smaller rule changes are to push through is shown in Forks & controversies. What a fixed money supply means economically, and what economists criticise about it, is explained in Digital scarcity.
Halving and price
Around every halving you’ll read headlines about rising prices: fewer new bitcoin with unchanged demand should push the price up. This gave rise to the theory of the four-year cycleGlossaryFour-year cycle (halving cycle)An observed pattern in which the bitcoin price has risen sharply roughly in step with the halvings and then fallen steeply. It is based on only four runs and is not a reliable buy or sell signal.On the learning path: Stage 3 · Step 3 – Returns & risk →In the glossary →. Arguments against it:
- The halving is known well in advance. In functioning markets, known information should already be priced in.
- Four events are too few for statistics. Other influences such as interest rates, regulation or large buyers cannot be separated out.
- New bitcoin are only a small part of supply. What matters most for the price is what the holders of existing bitcoin do.
That’s why we don’t make price forecasts. More on cycle theories in Holding for the long term.
What certainly changes is the situation for miners: their income from new bitcoin halves overnight, and less efficient machines often stop paying their way. How the network still keeps its ten-minute pace is explained in Mining & proof of work.
Quick check
Where is the cap of just under 21 million bitcoin actually set?
The final supply follows from the issuance schedule: 50 BTC per block, halved every 210,000 blocks. According to the code comment, MAX_MONEY is only a sanity check for individual amounts. Both are enforced by every node.
Frequently asked questions
What exactly is halved in the halving?
The amount of new bitcoin per block, i.e. the subsidy for miners. Your own bitcoin stay exactly as they are.
When is the next halving?
At block 1,050,000, probably in spring 2028. There is no fixed date, because blocks are found irregularly. The section ‘Where we stand today’ shows a continuously updated estimate.
Why aren’t there exactly 21 million bitcoin?
Bitcoin counts internally in whole satoshis. From the tenth halving onwards, halving no longer produces whole satoshis, and the remainder is cut off. That is why at most 20,999,999.9769 BTC will exist.
What happens after 2140?
No new bitcoin will be created; miners will receive only transaction fees. Whether that is enough to keep the network secure is an open question among experts.
Can the 21 million limit be raised?
Only if practically all users voluntarily run software with new rules. Anyone who changes the limit on their own creates a separate chain and therefore a different currency. There is no authority that could simply increase the supply.
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Sources9 sources · 4 publishers
The superscript numbers in the text refer to these sources.
- Bitcoin: A Peer-to-Peer Electronic Cash System – Satoshi Nakamoto, 31.10.2008 (accessed 28/09/2026)
- Bitcoin Core source code: src/validation.cpp (GetBlockSubsidy) – Bitcoin Core (accessed 28/09/2026)
- Bitcoin Core source code: src/kernel/chainparams.cpp (nSubsidyHalvingInterval) – Bitcoin Core (accessed 28/09/2026)
- Bitcoin Core source code: src/consensus/amount.h (COIN, MAX_MONEY) – Bitcoin Core (accessed 28/09/2026)
- Controlled supply – Bitcoin Wiki (accessed 28/09/2026)
- Value overflow incident – Bitcoin Wiki (accessed 28/09/2026)
- mempool.space block explorer – timestamps of blocks 0, 210,000, 420,000, 630,000 and 840,000 – mempool.space (accessed 28/09/2026)
- mempool.space API: current block height – mempool.space (accessed 28/09/2026)
- mempool.space API: Difficulty Adjustment (average block time) – mempool.space (accessed 28/09/2026)
This article is for education only and is not investment, tax or legal advice.