Satoshi

A satoshi, often shortened to sat, is the smallest unit of bitcoin that can be recorded on the blockchain. There are 100 million satoshis in one bitcoin, so 1 sat equals 0.00000001 BTC. The unit is named after Satoshi Nakamoto, the pseudonymous creator of Bitcoin.

Satoshis make it practical to talk about small amounts. If one bitcoin is worth 100,000 US dollars, then one satoshi is worth 0.001 dollars, and 10,000 sats are worth 10 dollars. Lightning Network payments and transaction fees are usually quoted in sats, and fee rates are given in satoshis per virtual byte of transaction data.

The total supply of bitcoin, 21 million coins, equals 2.1 quadrillion satoshis. Some people prefer to measure savings in sats because whole numbers feel more intuitive than long decimal fractions of a coin. There is no smaller on-chain unit, although the Lightning Network can track amounts in millisatoshis internally before settling to the base chain.