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What is a satoshi?
A satoshi is the smallest unit of bitcoin recorded on the blockchain. One bitcoin equals 100,000,000 satoshis, so one satoshi is 0.00000001 BTC.
What it means for you
Many wallets and fee screens show amounts in satoshis, often shortened to sats: 50,000 sats is 0.0005 BTC. Check which unit a field expects before sending, because BTC and sats differ by a factor of 100 million.
How it works
Bitcoin does not record fractions. Every transaction output carries its value as a whole number of satoshis, and the BTC figure a wallet shows is that number divided by 100,000,000. The fee is the difference between what the inputs spend and what the outputs pay, also counted in satoshis, and any amount left over beyond the payment returns to the sender as a change output. Because the block subsidy is computed in satoshis, it eventually halves to zero; nothing smaller than one satoshi can be recorded on the chain.
An example
Say a wallet shows 0.0015 BTC. That is 150,000 sats. Send 100,000 sats with a 2,000-sat fee and the transaction returns 48,000 sats to you as change, all counted in whole satoshis.
Sources: bitcoin.org: Vocabulary, Bitcoin developer glossary, Bitcoin developer guide: Transactions, BIP 42: A finite monetary supply for Bitcoin · checked 4 October 2026
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Educational content, not financial advice. Written by hand and checked against the source named above. Something wrong? Tell us and we reply within two business days.