What is satoshi?
The smallest unit of Bitcoin, one hundred-millionth of a coin (0.00000001 BTC).
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In this entry
The smallest unit of Bitcoin, one hundred-millionth of a coin (0.00000001 BTC).
It is named after Bitcoin's pseudonymous creator, Satoshi Nakamoto. Network fees and small payments are often quoted in satoshis rather than in whole bitcoin.
The unit exists because the protocol's internal accounting has always been in integers. There is no fractional Bitcoin at the software level; there are satoshis, and "one bitcoin" is a display convention for 100,000,000 of them. That ordering matters more than it sounds, because it means divisibility is not something that has to be added later.
How it works
- Every amount on chain is an integer number of satoshis. Balances, outputs, and fees are all counted this way, which avoids the rounding errors that decimal representations invite.
- Display is a wallet choice. Software converts to BTC, to satoshis, or to a local currency for presentation. The chain is unaffected by which you prefer.
- Fees are quoted per virtual byte in satoshis. A rate of 20 sat/vB on a 141-byte transaction is 2,820 satoshis. See sat vb and network fee.
- Very small outputs become uneconomic. An output worth less than the fee required to spend it is dust, and wallets and relays apply thresholds to discourage creating them.
- The unit is used natively elsewhere. lightning network payments are denominated in satoshis and below, because typical amounts are far smaller than a whole coin.
The total supply cap expressed in satoshis is 2,100,000,000,000,000, which is the figure the protocol actually works with.
Example
Simple conversions, worth checking once so the decimal places stop being confusing.
| Amount in BTC | Amount in satoshis |
|---|---|
| 1 | 100,000,000 |
| 0.01 | 1,000,000 |
| 0.001 | 100,000 |
| 0.00005 | 5,000 |
Exact conversions, not estimates.
Illustratively, if one Bitcoin is worth $60,000, one satoshi is $0.0006, and $10 is about 16,667 satoshis. A network fee of 2,820 satoshis is roughly $1.69 at that price. Quoting fees in satoshis is what makes them comparable across price levels: the byte cost of a transaction does not change when the exchange rate does.
Why it matters when you buy
You do not have to buy a whole coin, which is the misconception that keeps some people away entirely. Exchange minimums are typically a small amount of currency, and what you receive is simply a number of satoshis. Reading a withdrawal fee quoted in satoshis rather than in dollars also tells you what the transfer really costs. The fee comparison covers exchange charges and how to buy crypto covers the process.
Related terms
bitcoin — the coin this divides; sat vb — fee rates quoted in satoshis; network fee — what you pay per transaction; dust — outputs too small to spend; lightning network — payments denominated in satoshis; utxo — the outputs holding these amounts.
Questions
Do I have to buy a whole Bitcoin?
No. Bitcoin divides to eight decimal places, so exchanges sell fractions and your balance is simply a number of satoshis. Minimum purchase sizes are set by the venue, not by the protocol.
Why are fees quoted in satoshis instead of dollars?
Because the cost of a transaction depends on its size in bytes, not on the exchange rate. A satoshi rate stays meaningful across price levels, while a dollar figure changes daily without anything about the network changing.
Is a satoshi the smallest possible unit?
On chain, yes. The Lightning Network accounts internally in millisatoshis, a thousandth of a satoshi, but amounts settled to the Bitcoin chain are always whole satoshis.