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Satoshi converter
1 BTC = 100,000,000 sats. Type into either field.
Value at that price—
Tools
Three small calculators. Prices are whatever you enter — check a source you trust and type in today's number.
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Next halving
Estimated only — actual date drifts with network hash rate.
Target block1,050,000
Estimated date17 Apr 2028
Days—
Hrs / Min / Sec—
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Stacking plan
A forward-looking planning sketch, not a return projection. Not financial advice.
Total invested—
BTC acquired—
Sats acquired—
The book
The long-form version of this site, published chapter by chapter.
Twenty-One Million: Bitcoin, in Plain Arithmetic
Where the cap comes from, what a satoshi is, why the schedule holds — explained with arithmetic you can check on paper, not opinions. New chapters added regularly.
Start with Chapter 1: Why 21 Million? →Terms, plainly
No jargon left unexplained on purpose.
- Satoshi (sat)
- The smallest unit of bitcoin — one hundred-millionth of a BTC. Named after Bitcoin's pseudonymous creator.
- Halving
- Every 210,000 blocks (~4 years), the reward paid to miners for adding a block is cut in half. This is what makes the 21 million cap hold.
- UTXO
- "Unspent transaction output" — bitcoin doesn't track account balances, it tracks discrete chunks of coin you can spend, like bills in a wallet.
- Self-custody
- Holding your own private keys instead of leaving coins on an exchange. More responsibility, no counterparty to fail.
- Seed phrase
- The 12–24 words that recreate your wallet. Never type it into a website, an app, or tell it to anyone who asks — including us. Anyone who has it has your coins.
- Lightning Network
- A second layer built on top of Bitcoin for fast, cheap, small payments — the kind a tip jar actually needs.
- Cold storage
- Keeping private keys on a device that's never connected to the internet. Slower to use, much harder to steal.
- HODL
- Originally a 2013 forum typo for "hold," now shorthand for holding through volatility rather than trading on it.
Common questions
Answered with arithmetic, not opinions.
Why is bitcoin capped at 21 million?
The cap is a consequence of two rules written into the protocol: a block is added roughly every 10 minutes, and the coins issued per block are cut in half every 210,000 blocks. Start at 50 BTC per block and keep halving, and the total issuance converges on just under 21,000,000 BTC. It's arithmetic, not a decree.
How many satoshis are in one bitcoin?
Exactly 100,000,000 satoshis (sats) make one bitcoin. A satoshi is the smallest unit the protocol can track, so all 21 million BTC amount to 2.1 quadrillion sats.
Is all 21 million bitcoin already mined?
No. Over 19.7 million BTC have been issued, but new coins keep arriving with every block, at a rate that halves roughly every four years. Because issuance shrinks geometrically, the final satoshi isn't expected to be mined until around the year 2140.
When is the next halving?
At block 1,050,000, currently estimated for spring 2028 — the countdown above tracks it. The date is an estimate only: blocks average 10 minutes but drift with network hash rate, so the calendar date moves while the block number does not.
Can the 21 million cap be changed?
Technically the software could be forked to issue more coins — but every node operator would have to voluntarily adopt the change, and holders have a direct incentive to refuse, since more supply would dilute them. A version with a raised cap would simply be a different network that people can decline to use.
Will there be exactly 21 million?
Slightly less, twice over. The geometric schedule tops out just short of 21,000,000 (about 20,999,999.97 BTC), and a meaningful amount on top of that — commonly estimated in the millions of BTC — is permanently lost to discarded keys, making the spendable supply smaller still.
Keep this page running
Everything above is free, always. If it was useful, a tip is welcome and never expected.
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