Network fee (gas)
A network fee (gas) is what you pay to have a transaction processed on a blockchain such as Ethereum. Validators earn it, and it rises when the network is busy.
How it works
On Ethereum every operation needs computing work, measured in units of gas. A simple ETH transfer uses 21,000 gas, while a DEX swap or smart contract call uses more. The total fee is gas used × gas price, and the price is quoted in gwei (one billionth of an ETH).
The gas price has a base fee, which the network burns, plus a tip (priority fee) for the validator. When lots of people want in, the base fee climbs and transactions get pricier. If you set the price too low, the transaction can sit in the mempool for a long time.
You pay the fee in the network's own coin: ETH on Ethereum, and each other chain's native coin elsewhere. So even to send USDT you need a little of the native coin in your wallet. Transfers are cheapest when the network is quiet or on Layer 2 networks.
An ETH transfer needs 21,000 gas. At 20 gwei the fee is 21,000 × 20 = 420,000 gwei, or 0.00042 ETH. If the gas price spikes to 100 gwei at peak time, the same transfer costs 0.0021 ETH, five times more.
A common mistake is holding only tokens (like USDT) with none of the network's coin, and then being unable to send them. Another is setting the gas limit too low: a failed transaction still charges a fee. Keep a small buffer of the native coin and stick with the gas values your wallet suggests.
Questions and answers
What is a gas fee in simple terms?
It is what the network charges to process your transaction. The more complex the action and the busier the network, the higher it is.
Why are Ethereum gas fees sometimes so high?
When many people send transactions at once, the base gas price goes up. Complex actions like DEX swaps also use more gas than a simple transfer.
Do I pay gas if a transaction fails?
Yes. If a transaction fails after it reaches the network, the gas used is not refunded, because the network already did the work.
Related terms
Read next
A USDT transfer takes a couple of minutes, but one mistake with the network or address can cost the whole amount. Here is how to…
Read →How to buy your first crypto: a step-by-step guideStep by step, from picking an exchange to coins sitting in your own wallet. No leverage, no shortcuts, and a check at every step.
Read →NFTAn NFT (non-fungible token) is a unique blockchain record tied to a specific item, such as an image. Two NFTs cannot…
Updated: 2026-10-19