Entries → coin profiles
Bitcoin: History, Supply Schedule, and Key Numbers
The reference entry for Bitcoin. Fixed parameters, the issuance schedule, and the figures that do not change.
| Entry type | reference |
|---|---|
| Section | coin profiles |
| Last verified | |
| Compiled by | Reference Desk |
Entry last verified May 2026. Protocol parameters below are fixed by consensus rules and do not change without a network-wide upgrade.
Fixed parameters
| Parameter | Value |
|---|---|
| Launch | January 2009 |
| Consensus | Proof of work, SHA-256 |
| Target block interval | 10 minutes |
| Difficulty adjustment | Every 2,016 blocks, approximately two weeks |
| Maximum supply | 21,000,000 BTC |
| Smallest unit | 1 satoshi, 0.00000001 BTC |
| Halving interval | Every 210,000 blocks, approximately four years |
Issuance schedule
The block subsidy began at 50 BTC and halves every 210,000 blocks.
| Period | Block reward |
|---|---|
| 2009 to 2012 | 50 BTC |
| 2012 to 2016 | 25 BTC |
| 2016 to 2020 | 12.5 BTC |
| 2020 to 2024 | 6.25 BTC |
| 2024 to 2028 | 3.125 BTC |
| 2028 to 2032 | 1.5625 BTC |
Issuance continues until the reward rounds to zero, projected around the year 2140. After that, miner revenue comes entirely from transaction fees.
The fee transition
The security budget currently comes mostly from issuance. As the subsidy halves, fees must replace it or the cost of attacking the network falls.
Fee revenue has spiked during periods of congestion and has not yet formed a durable base. Whether it will is the principal open question about the network’s long-term security model, and it has no settled answer.
Supply notes
The circulating figure is not the available figure.
A material share of mined coins are believed permanently lost through discarded keys, particularly from the earliest years. Estimates vary widely and none is authoritative, because a lost coin and a patiently held coin are indistinguishable on-chain.
A large tranche mined in 2009 and attributed to the network’s creator has never moved.
Key protocol upgrades
| Upgrade | Year | Effect |
|---|---|---|
| P2SH | 2012 | Enabled more complex spending conditions |
| SegWit | 2017 | Restructured transaction data, increased effective capacity |
| Taproot | 2021 | Improved privacy and efficiency for complex spends |
Bitcoin’s upgrade cadence is deliberately slow. Changes require broad consensus and are generally soft forks, preserving compatibility for nodes that do not upgrade.
What this entry does not cover
Price, market capitalisation or forecasts. Those change continuously and are available from any market data source.
For current spot pricing and depth, use the venues directly rather than aggregated figures, which have historically included inflated volume from smaller platforms. Pairs are quoted by exchanges quoting a direct fiat pair among others.
Figures in this entry were correct on the date shown. Spotted something out of date?Send a correction and the entry gets updated.