Fee estimation is both an art and a science, relying on mempool analysis and recent fee market data. Wallets often query node-based fee estimators or third-party services to guess how many satoshis per vByte you should pay to get included in the next block or within a handful of blocks.

During periods of heavy congestion, these estimates can spike rapidly, sometimes overshooting actual requirements. Conversely, low-activity periods might see recommended fees drop near the default relay minimum. It’s rarely exact—many wallets allow either manual overrides or dynamic adjustments if the transaction remains unconfirmed longer than expected.