Fee Rate (sat/vB)

Fee rate, quoted in satoshis per virtual byte (sat/vB), is the price a sender offers for each unit of block space their transaction consumes. It is what miners actually rank transactions by: a transaction's total fee is its size in virtual bytes multiplied by its fee rate, and because block space is limited, miners fill blocks with the highest-paying transactions first.

What a virtual byte is

Since the SegWit upgrade, transaction size is measured in weight units, where one virtual byte equals four weight units. The virtual size (vsize) discounts witness data such as signatures, so SegWit transactions occupy fewer virtual bytes than their raw byte count and cost less to confirm. Quoting fees in sat/vB lets everyone compare transactions on the same per-space basis regardless of their internal structure.

Choosing a fee rate

During quiet periods a low sat/vB clears quickly; when the mempool is congested, only transactions above the prevailing market rate get mined promptly, and underpaid ones can wait hours or days. Fee estimators read the mempool to suggest a rate for a target confirmation window. Paying more buys faster inclusion, not greater finality.

Fee rate is denominated in the network's base unit, so it builds directly on the satoshi (unit), and paying a competitive rate is what gets a transaction its first confirmation sooner.

See current fees in live network vitals (mempool fees).