Satoshi
Smallest standard unit of Bitcoin, equal to 0.00000001 BTC.
A satoshi, commonly shortened to sat, is the smallest standard unit recorded for Bitcoin amounts. One satoshi equals 0.00000001 bitcoin, and 100,000,000 satoshis equal one BTC. The unit is named after Bitcoin's pseudonymous creator, Satoshi Nakamoto.
Bitcoin software represents transaction outputs as whole numbers of satoshis rather than floating-point BTC values. This avoids ambiguous decimal rounding in consensus-critical accounting. A wallet may display the same balance as 0.0025 BTC or 250,000 sats, but the underlying value on the blockchain is identical. The denomination is a user-interface choice.
Sats matter because a single bitcoin can have a high market price while remaining divisible for small payments. A coffee purchase, Lightning Network payment, or mining fee is often easier to understand in sats. Expressing prices in smaller units can also reduce the mistaken impression that someone must buy one complete bitcoin. Users can acquire and transfer fractions, subject to fees and service minimums.
Transaction fees use related terminology. Bitcoin fee rates are commonly quoted in satoshis per virtual byte, written sat/vB. This measures how much a sender offers relative to the transaction's weighted size. It is not the same as the total fee. A 200-vB transaction at 5 sat/vB pays 1,000 sats, while wallet estimates change with network demand.
The protocol can represent values below one satoshi in some off-chain systems. Lightning implementations may account internally in millisatoshis, but final settlement on the Bitcoin base layer must use whole satoshis. These smaller accounting units do not change Bitcoin's on-chain divisibility. Applications must handle rounding explicitly when opening, updating, or closing payment channels.
Fiat value is not fixed. The purchasing power of one sat changes with Bitcoin's market price, so the same number of sats may represent a very different local-currency amount over time. Invoices should state exchange-rate source, quote time, and expiration when converting between units. Accounting systems should preserve the exact Bitcoin amount alongside any historical fiat valuation.
Common mistakes include confusing BTC and sats, reading a fee rate as a total, or trusting a rounded fiat display. Before sending, verify the selected denomination, recipient, total amount, and network fee. Businesses should store exact integer amounts and apply clear rounding rules. A satoshi makes Bitcoin practical at small scales, but careful unit labeling is essential whenever wallets, exchanges, invoices, or accounting systems exchange values.
Frequently asked questions
- Satoshis make small Bitcoin prices and payments easier to read without long strings of leading zeros. A fee of 500 sats is clearer than 0.00000500 BTC for many users. Display preference does not change the underlying amount. Wallets may also quote mining fees in satoshis per virtual byte, which is a rate rather than a total payment amount.
- One bitcoin equals exactly 100,000,000 satoshis under Bitcoin's standard unit convention. Therefore, 100,000 sats equals 0.001 BTC and one million sats equals 0.01 BTC. Wallet software handles the integer accounting, but exchange displays may round decimal values. Confirm the complete amount and fee before sending because visual rounding can hide a meaningful difference.
- Many Bitcoin wallets let users choose BTC, mBTC, bits, or sats in display or denomination settings. Exchanges and portfolio apps vary, and some show a local-currency estimate alongside Bitcoin units. Changing the display does not convert or move funds. Confirm which unit is selected before entering an amount, especially when copying payment requests between applications that use different defaults.