What is a Satoshi (Sat)?
The smallest unit of bitcoin, equal to 0.00000001 BTC. Named after Bitcoin's creator. One bitcoin equals 100 million satoshis.
Why It Matters
The satoshi makes Bitcoin practically divisible for future use. While Bitcoin's fixed supply of 21 million coins might seem limited for a global currency, the subdivision into 100 million satoshis per bitcoin creates effectively 2.1 quadrillion satoshis. This ensures Bitcoin can function as currency even if BTC prices become very high. Satoshis are also the standard unit for measuring transaction fees (typically in satoshis per byte or satoshis per virtual byte). When Bitcoin advocates talk about "stacking sats," they mean accumulating satoshis, emphasizing gradual accumulation rather than thinking in whole bitcoins. The satoshi unit connects Bitcoin's history (named after creator Satoshi Nakamoto) to its practical present as divisible currency. As Bitcoin's price has grown, thinking in sats rather than whole BTC has become increasingly common—some exchanges and wallets now display balances in satoshis by default.
How It Works
One satoshi is the atomic unit of Bitcoin—you cannot subdivide it further in the current protocol (though this could theoretically change with a future upgrade like the Lightning Network's millisatoshis, which exist only off-chain). When you see transaction fees, they're quoted in satoshis per byte of transaction data (or sat/vB after SegWit). A 250-byte transaction at 50 sat/byte costs 12,500 satoshis total (0.000125 BTC). Wallets handle satoshi conversion automatically, showing you prices in satoshis or bitcoin depending on context. For perspective, at a price of $100,000 per bitcoin, one satoshi equals $0.001—one-tenth of a cent. This level of divisibility means Bitcoin can handle micropayments that traditional payment systems cannot process economically.