A satoshi, or sat, is a denomination of Bitcoin that has been broken down into a smaller amount, named after the pseudonymous creator of Bitcoin, Satoshi Nakamoto. Just as 100 cents make up a dollar, 100,000,000 satoshis make up 1 Bitcoin. It is a measure used most commonly in calculating transaction fees, or Bitcoin transactions of smaller amounts. 1 Bitcoin = 100,000,000 sats