Learn / How it works · 5 of 5
Fees and the mempool
Each block has limited room. When many people want in, they bid with fees.
- Waiting transactions sit in the mempool, a kind of waiting room.
- Miners pick the ones paying the most for their size first.
- Your fee depends on the size of the transaction in data, not the amount you send.
Fees are quoted in sats per virtual byte, written sat/vB. A vbyte is a measure of a transaction's size in data. A simple payment is around 140 vbytes, so at 5 sat/vB the fee is about 700 sats. Sending $10 or $10 million can cost the same.
When the network is quiet, a low fee confirms in the next block or two. When it is busy, low-fee transactions wait. Most wallets suggest a fee for you based on how fast you want it to go.
Check live fees at mempool.space. For everyday small payments, Lightning is usually far cheaper.
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Want to go deeper?
My transaction is stuck. What now?
Wait, or bump it. Many wallets offer "Replace-By-Fee" to resend the same payment with a higher fee. Unconfirmed transactions that never confirm eventually drop out, and the coins stay yours.
Why are some transactions bigger?
Size depends on how many coins, or "inputs," you combine. Paying from many small deposits makes a bigger transaction than paying from one large one.