What is a Satoshi (Sat)?

A satoshi, often shortened to "sat," is the smallest unit of bitcoin. One bitcoin contains exactly 100 million satoshis, so a single satoshi equals 0.00000001 BTC. The unit takes its name from Bitcoin's pseudonymous creator, Satoshi Nakamoto.

A dollar divides into 100 cents. A bitcoin divides into 100,000,000 satoshis. That level of divisibility means you can use bitcoin for a coffee purchase or a cross-border settlement with equal precision.

Why It Matters

Bitcoin has a fixed supply of 21 million coins. With 100 million sats per coin, the total supply reaches 2.1 quadrillion satoshis. Every person on Earth could transact in bitcoin daily and still have plenty of units to go around, regardless of the price per coin.

You do not need to buy a whole bitcoin. Most holders accumulate small amounts over time, a habit the Bitcoin community calls "stacking sats." Once you start counting in satoshis instead of whole coins, the price tag stops being intimidating. See what consistent stacking could have returned with the DCA Calculator. You can check how many sats your dollars buy right now with the Sats Per Dollar tool, or convert between units with the Bitcoin Unit Converter.

How It Works

The Bitcoin network tracks all amounts in satoshis. When your wallet displays "0.005 BTC," the protocol records 500,000 satoshis. One satoshi is the smallest amount you can send in a standard on-chain transaction. The protocol does not subdivide further.

Transaction fees also use satoshis as their unit. You pay in satoshis per virtual byte (sat/vB), which reflects how much block space your transaction occupies. A typical transaction runs about 140 virtual bytes. At a fee rate of 10 sat/vB, that costs roughly 1,400 satoshis. Your wallet calculates this for you, but knowing the unit helps you read fee estimates.

On the Lightning Network, Bitcoin's layer-2 payment system, you can transact in amounts smaller than a satoshi. Lightning tracks "millisatoshis" (one thousandth of a sat) internally, though final settlement on the main chain rounds to whole satoshis. That extra precision makes very small payments practical where they would not be on-chain.

Satoshi (sat)