What is a Bitcoin transaction fee?
The transaction fee is the difference between the bitcoin used as transaction inputs and the bitcoin assigned to its outputs. The miner who includes that transaction in a valid block can collect the difference.
It is not a fee charged by a bank or a Bitcoin company. An exchange may also charge a separate withdrawal fee, which does not necessarily equal the actual network fee.
See also how miners are rewarded.
Why does the amount of bitcoin sent not determine the fee?
Bitcoin network fees depend on transaction data size, not simply whether you transfer $10 or $1,000 worth of bitcoin.
A transaction using many small unspent outputs (UTXOs) can take more data than one using a single input, even when the amount sent is smaller. That is why payments of equal value can have different fees.
What does sat/vB mean?
Wallets often show fees as sat/vB: satoshis per virtual byte. This is the fee rate, not the total fee.
For example, a transaction measuring 150 vB at 10 sat/vB would pay 1,500 sats in total. The actual fee depends on the size of your particular transaction.
Why do Bitcoin fees go up and down?
Blocks have limited capacity. When many transactions are waiting in the mempool, they often compete for space in the next blocks.
Miners have an economic incentive to select valid transactions with higher fee rates, subject to block constraints and their own selection policies. There is no guaranteed order or fixed market price.
The illustration uses 2, 10, and 30 sat/vB only as examples, not live recommendations or fixed tiers. Green indicates the lowest fee, not the fastest confirmation.
What if I choose a very low fee?
Your transaction might stay unconfirmed for a long time if block space is in demand. Some nodes may eventually drop it from their mempools.
Depending on your wallet and the transaction, a higher-fee replacement (RBF) or a technique such as CPFP may help. These methods are not always available and do not guarantee immediate confirmation.
Watch our short video on what one confirmation means.
How can I check current network fees?
Before sending, review your wallet’s fee estimates and compare them with current mempool.space conditions. Fee estimates change and cannot promise confirmation at a particular time.
Always check the recipient address, the amount, and the full transaction fee before authorizing a payment. You do not need to overpay for every transfer, but extremely low fees can mean a long wait.
For practical steps, read our mempool.space guide and how to send bitcoin with BlueWallet.