Each block has limited space, so miners pick the transactions that pay the most per unit of size. Your fee is therefore a bid for space, measured as a feerate in sat/vB.
What decides the cost
- Size, not amount: more inputs make a bigger transaction. Many small coins (UTXOs) cost more to spend.
- Demand: when the mempool is full, the price goes up.
- Urgency: you choose how fast you need it.
Reading the estimates
Wallets and explorers show tiers like "next block", "30 minutes", "1 hour" and "economy". As of 23 October 2026 the mempool is quiet: next block about 2 sat/vB, everything else about 1 sat/vB. In busy periods rates can be many times higher.
Bitcoin Core relays transactions down to a minimum of 0.1 sat/vB (100 sat/kvB), but a rate that low can wait a long time when blocks are full.
Practical tips
- Not urgent? Pick the economy rate.
- Consolidate small coins when fees are low.
- Use lightning network for small frequent payments.
- Use a wallet that supports rbf.
Stuck transaction?
- Replace-by-fee (rbf): the sender re-sends the same payment with a higher fee. Core has accepted replacements by default since version 28.0.
- Child-pays-for-parent (cpfp): the receiver spends the unconfirmed coin with a high fee, pulling the parent along.
A transaction that never confirms can eventually drop out of mempools, and the coins remain yours.
Takeaway
Check the mempool, pay for the speed you need, and use RBF if you guessed too low.