Bitcoin Basics · 1:36
The 21 Million Rule
Why can there never be more than 21 million bitcoin? In about 90 seconds, Steady explains how new bitcoin is created, why the reward is cut in half every four years, and how the total supply flattens just under 21 million.
Numbers in this episode
- ~10 min
- Average time between blocks. The network adjusts mining difficulty every 2,016 blocks to hold this pace.
- 210,000
- Blocks between halvings, which works out to about four years.
- 50 → 3.125
- Block reward in 2009 versus after the April 2024 halving. The next cut, to 1.5625 BTC, is expected around 2028.
- ≈ 20.1M
- Bitcoin mined by October 2026, estimated from the issuance schedule. That is about 96% of the cap.
- ≈ 2140
- When the last fraction of a bitcoin is expected to be mined.
- Satoshi Nakamoto, “Bitcoin: A Peer-to-Peer Electronic Cash System”, section 6, “Incentive” (Nakamoto Institute copy)
- Bitcoin protocol rules: about 10-minute block target, difficulty adjusted every 2,016 blocks
- Protocol rules (block subsidy schedule): 50 BTC at launch, halved every 210,000 blocks
- Bitcoin halving of April 2024 (block 840,000): subsidy 6.25 to 3.125 BTC
- Next halving to 1.5625 BTC at block 1,050,000; date estimated from block times
- Computed from bitcoin's issuance schedule: about 20.1 million mined by October 2026, last fraction around 2140
Transcript
Read the narration
Bitcoin has a hard limit: no more than 21 million coins can ever exist. Here's how that works.
About every 10 minutes, the network adds a new block of transactions to the chain.
Whoever adds the block earns brand-new bitcoin. In January 2009, that reward was 50 bitcoin per block.
Every 210,000 blocks, about every four years, the reward is cut in half. This is called the halving.
50 became 25, then 12.5, then 6.25. The April 2024 halving cut it to 3.125. The next one, around 2028, takes it to 1.5625.
Add up all those shrinking rewards, and the total climbs fast, then flattens just under 21 million.
By October 2026, about 20.1 million bitcoin have been mined. The last tiny fractions arrive around the year 2140.
Many currencies can expand their supply when a central bank decides to.
Bitcoin's schedule is written into its software, and thousands of independent computers reject any block that breaks the rules.
So remember: a new block about every 10 minutes, a halving every 210,000 blocks, and a hard cap of 21 million. See you next episode!