Supply, Issuance and the Halving
Calculate how Bitcoin's supply grows, why it approaches 21 million and what the halving changes.
What you will learn
- How new bitcoin are issued through the block reward
- How the halving schedule leads to the 21 million cap
- When the most recent halving happened and roughly when the next is expected
- Why the halving is not a reliable price signal
Explanation
Issuance means the creation of new coins. In Bitcoin, new coins are created only as part of the block subsidy, the new-coin part of the block reward a miner receives (the other part is transaction fees).
Every 210,000 blocks, the subsidy is cut in half. This event is called the halving. At about 144 blocks per day, 210,000 blocks take roughly four years, but the exact date depends on how fast blocks are found.
| Block heights | Subsidy per block | New BTC in this era |
|---|---|---|
| 0 – 209,999 | 50 BTC | 10,500,000 |
| 210,000 – 419,999 | 25 BTC | 5,250,000 |
| 420,000 – 629,999 | 12.5 BTC | 2,625,000 |
| 630,000 – 839,999 | 6.25 BTC | 1,312,500 |
| 840,000 – 1,049,999 | 3.125 BTC | 656,250 |
The most recent (fourth) halving took place at block 840,000 on 20 April 2024 shortly after midnight UTC (Coordinated Universal Time), which was still 19 April in the Americas. The subsidy fell from 6.25 to 3.125 BTC. The next halving is expected at block 1,050,000, roughly in 2028; the exact date is not known in advance.
Because each era adds half as much as the one before, the total gets closer and closer to 21 million but never goes above it. The smallest unit of bitcoin is the satoshi (0.00000001 BTC). Due to rounding to whole satoshis, the final total will be slightly below 21 million, and issuance is expected to end around the year 2140.
After the subsidy ends, miners will depend only on transaction fees. Whether fees will be enough to keep the network secure is an open question.
Some people link halvings with past price rises. This is a historical observation based on very few events, not a rule. Many other factors move prices.
Worked example
Hypothetical example: calculating supply and the annual issuance rate.
Assumptions: exactly 144 blocks per day; we use a round, hypothetical circulating supply of 19.9 million BTC for the rate calculation. Lost coins are ignored.
- Total issued up to block 840,000: 10,500,000 + 5,250,000 + 2,625,000 + 1,312,500 = 19,687,500 BTC.
- New coins per day in the current era: 144 × 3.125 = 450 BTC.
- New coins per year: 450 × 365 = 164,250 BTC.
- Annual issuance rate: 164,250 ÷ 19,900,000 ≈ 0.00825 = about 0.83% per year.
- After the next halving: 144 × 1.5625 = 225 BTC per day, half the current amount.
Excluded: transaction fees (they are not new coins) and coins that are lost forever, which reduce the usable supply.
Common mistake
Practice activity
(a) How many BTC will be issued in the era that starts at block 1,050,000 (subsidy 1.5625 BTC)? (b) What will the total issued supply be at block 1,260,000? (c) How many satoshis are 0.5 BTC?
Show solution
(a) 1.5625 × 210,000 = 328,125 BTC.
(b) 19,687,500 + 656,250 + 328,125 = 20,671,875 BTC.
(c) 0.5 × 100,000,000 = 50,000,000 satoshis.
Limitations: real block times vary, so era lengths in years are only approximate.
Key takeaways
- New bitcoin come only from the block subsidy, which halves every 210,000 blocks.
- The most recent halving was at block 840,000 in April 2024; the subsidy is now 3.125 BTC.
- The next halving is expected roughly in 2028 at block 1,050,000.
- A known supply schedule does not make future prices predictable.
Next step
In the next lesson, you will learn how wallets, private keys and seed phrases control access to bitcoin.
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