Guide

How Are Bitcoin Fees Calculated?

Bitcoin fees are not calculated as a percentage of the transfer amount; they depend primarily on the block space occupied by the transaction.

Core Formula

Fee = transaction virtual size in vB × fee rate in sat/vB

If a transaction is 180 vB and the fee rate is 12 sat/vB, the fee is approximately 2160 satoshi.

If your wallet balance is spread across many small UTXOs, spending them requires more inputs, increasing the transaction size and therefore the fee.

For transactions that are not urgent, you can choose a lower sat/vB rate.
During network congestion, low-fee transactions may remain unconfirmed for a long time.
It is best to consolidate UTXOs when the network is not congested.