Satoshi

A bitcoin is made of 100,000,000 satoshis, often called sats. Wallets usually show amounts in bitcoin, but the network only knows satoshis: in Bitcoin Core’s code, every amount is a whole number of them, and a bitcoin is defined as 100,000,000.

The name pays homage to bitcoin’s creator, Satoshi Nakamoto. In February 2011, a user of the Bitcointalk forum suggested “satoshi” as a nickname for the small units, and it stuck.

Nothing smaller exists on the network, and that shapes two things:

• The supply. The new bitcoin each block creates are counted in satoshis, and halve about every four years. Since the halving of April 2024, a block creates 312,500,000 satoshis, or 3.125 bitcoin. When a halving would leave a fraction of a satoshi, the fraction is dropped, and after the 33rd, around 2140, nothing is left. That’s why the total stops just short of 21 million, as the guide on how many bitcoin will ever exist explains.
• The fees. Wallets quote the network fee in satoshis per virtual byte, a measure of a transaction’s size. Over the year to October 2026, a typical transaction paid about 1 satoshi per virtual byte, according to mempool.space, and a simple payment takes about 140 virtual bytes, according to bitcoin.org: about 140 satoshis, whatever the amount sent.

Owning bitcoin doesn’t take a whole one. What a wallet holds is a count of satoshis.