Gas fees
Fees paid to the network to run a transaction or contract, set by demand for block space.
Paying for space in a block
Every operation on Ethereum uses an amount of “gas”, a unit of computation: a simple ETH transfer costs 21,000 units, a swap on a decentralised exchange much more. The price of each unit, in gwei (a billionth of an ETH), rises when many users want into the same block.
The price has a base fee, set by the protocol and burned, and a tip paid to the validator to get in faster.
Frais = gaz consommé × (frais de base + pourboire)
- 1 gwei = 0.000000001 ETH
Worked example
The cost of an ETH transfer
- Gas used: 21,000 units.
- Price: 20 gwei (18 base and 2 tip).
- Fee: 21,000 x 20 = 420,000 gwei, i.e. 0.00042 ETH.
- With ETH at $3,000: $1.26.
The same transfer can cost ten times more during an activity spike.
Common mistakes
- Setting too low a gas limit: the transaction fails and the gas used is still paid.
Questions and answers
Why are fees lower on layer 2s?
They batch thousands of transactions and write only a summary to Ethereum: the cost is shared among all.
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