Crypto glossary
Satoshis per vbyte (sat/vB)
Satoshis per virtual byte (sat/vB) is the unit for Bitcoin fee rates: the fee divided by the transaction's size in vbytes, used by miners to rank it.
Bitcoin fees depend on how much block space a transaction uses, not on the amount sent. Since SegWit, size is measured in weight units: each non-witness byte counts four units and each witness byte, mostly signatures, counts one. Dividing weight by four gives virtual bytes. A block can hold four million weight units, or one million vbytes.
Wallets and mempool explorers express fee rates in sat/vB. Multiply the rate by the transaction's vsize to get the total fee: a typical one-input, two-output native SegWit payment is about 141 vB, so at 10 sat/vB it costs around 1,410 satoshis. Fee estimators show the rate needed to confirm in the next block, within an hour or within a day.
The witness discount is why modern address types are cheaper: spending a legacy output takes more vbytes than spending a native SegWit or Taproot one. Transactions with many inputs cost more, which is why consolidating small UTXOs during quiet periods saves money. Rates can swing from 1 sat/vB to several hundred within days.
Example
A wallet suggests 25 sat/vB for next-block confirmation; for a 200 vB transaction that means a fee of 5,000 sats, regardless of whether it moves 0.01 or 50 BTC.