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Satoshi converter
1 BTC = 100,000,000 sats. Type into either field.
Value at that price—
Tools
Five free tools: four small calculators plus a real cost-basis tracker. Prices are whatever you enter — check a source you trust and type in today's number.
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Bitcoin halving countdown
Estimated only — actual date drifts with network hash rate.
Target block1,050,000
Estimated date17 Apr 2028
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Stacking plan
A forward-looking planning sketch, not a return projection. Not financial advice.
Total invested—
BTC acquired—
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Halving era lookup
Enter any block height to see its halving era and reward. Uses the schedule, not a live node.
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Reward at that height—
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Blocks until next halving—
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DCA cost-basis tracker
A real tool, not a calculator: log every buy, watch your average cost basis update, export a CSV for tax season. Saved in your browser only.
Ready to hold your own keys?
The tools above work with numbers you type in. Self-custody means the coins are actually yours.
Choosing a Hardware Wallet
Trezor, BitBox02, and Coldcard, compared plainly — open-source status, price, coin support, and who each one actually fits. Includes an explanation of why one well-known brand is deliberately left off the list.
Compare hardware wallets →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? →All 24 chapters are published — see the full contents. More may be added later.
Terms, plainly
No jargon left unexplained on purpose — each term links to the chapter that goes deeper.
- Fixed supply
- A currency whose total issuance is capped and can't be increased at will — the opposite of a central bank managing supply. The honest case for both fixed and managed supply, argued fairly.
- Satoshi (sat)
- The smallest unit of bitcoin — one hundred-millionth of a BTC. Named after Bitcoin's pseudonymous creator. Why the sat, not the BTC, is the unit that actually matters.
- Block
- The batch of transactions Bitcoin bundles and confirms roughly every 10 minutes — the network's clock. How that ten-minute average actually holds.
- Difficulty adjustment
- Every 2,016 blocks, the network retunes how hard mining is, so blocks keep arriving roughly every 10 minutes no matter how much hashing power joins or leaves. A real historical retarget, worked through.
- 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. Every halving, past and projected, on one table.
- Mining
- Spending real computing power to add the next block and collect its reward. Why anyone still bothers as the reward keeps shrinking, and what happens if you try it yourself.
- Proof-of-work
- Bitcoin's consensus rule: earn the right to add the next block by spending real, externally-verifiable electricity and hardware, not by holding coins or a vote. How it compares to proof-of-stake and other mechanisms.
- Full node
- Software that independently checks every rule of every block and transaction, rather than trusting someone else's word for it. How anyone can audit the entire 21 million supply themselves.
- Private key
- The secret number that lets you sign a transaction — the actual thing that makes bitcoin yours, full stop. Never type it into a website, an app, or tell it to anyone who asks — including us. Anyone who has it has your coins. What "owning" bitcoin actually reduces to.
- 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. Why this one rule outranks every other rule in Bitcoin.
- Self-custody
- Holding your own private keys instead of leaving coins on an exchange. More responsibility, no counterparty to fail. Hot vs. cold, custodial vs. non-custodial — the full taxonomy, or jump straight to which device actually fits you.
- Cold storage
- Keeping private keys on a device that's never connected to the internet. Slower to use, much harder to steal. Where cold storage fits among the other wallet types, or see how the actual devices compare, side by side.
- UTXO
- "Unspent transaction output" — bitcoin doesn't track account balances, it tracks discrete chunks of coin you can spend, like bills in a wallet. The full chapter on how that actually works.
- Lightning Network
- A second layer built on top of Bitcoin for fast, cheap, small payments — the kind a tip jar actually needs. How it actually works.
- Dollar-cost averaging (DCA)
- Buying a fixed dollar amount on a regular schedule instead of trying to time the market. Track your own cost basis with the free tracker.
- HODL
- Originally a 2013 forum typo for "hold," now shorthand for holding through volatility rather than trading on it.
- Pseudonymous
- Not tied to a real name by the protocol itself, but every transaction is permanently public — a different, more exposed thing than truly anonymous. What Bitcoin's public ledger actually reveals, and what genuinely helps.
- Wrapped Bitcoin
- A token on another blockchain meant to always be redeemable 1-for-1 for real BTC held by a custodian — the usual way BTC's value reaches DeFi contracts Bitcoin's own script can't run. The mechanics, and the honest risk history.
- Inelastic supply
- A supply that doesn't respond to price — Bitcoin's issuance schedule is the same whether the price is high or low, unlike a mine that can ramp up production when it's profitable to. Why that's a big part of why the price moves the way it does.
- Hedge
- An asset expected to hold or gain value specifically when something else — inflation, a stock-market selloff — is losing it. Bitcoin was pitched as one; the price data since 2024 tells a more mixed story. Why correlation with stocks rose, and what that does to the hedge argument.
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 — see the full derivation.
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 — why that's the unit that actually matters.
Is all 21 million bitcoin already mined?
No, but the majority has been. As of the audited count in Chapter 7, over 19.7 million BTC had already been issued, with new coins arriving 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. Every halving, past and projected, on one table.
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. The two rules that make this hold.
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. See every major loss estimate, sourced and compared.
How much bitcoin has been lost forever?
Depends which "lost" you mean. Provably destroyed (sent to unspendable burn addresses): about 3,200 BTC — the only hard floor, everything else is a probability model. The most-cited forensic estimate, Chainalysis, puts probably-lost coins at roughly 2.78–3.79 million BTC. The broadest measure, Glassnode's coins untouched for 7+ years, runs to about 5.25 million BTC — though that band also counts long-term holders who aren't actually lost. Every estimate, sourced and compared side by side.
21 million divided by 8 billion people — how much is that?
21,000,000 BTC divided by 8,000,000,000 people equals 0.002625 BTC, or 262,500 satoshis per person. That's 0.2625% of one bitcoin each — just over a quarter of one percent, not a quarter of a bitcoin. This is a hypothetical equal split using eight billion people, not a current population estimate or a forecast of ownership; some coins are lost and holdings are uneven. See the full derivation.
Keep this page running
Everything above is free, always. If it was useful, a tip is welcome and never expected.
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