Gas is the fee you pay to execute a transaction on a blockchain. On Ethereum and EVM chains, every action — sending tokens, swapping, approving a contract — consumes gas units and costs the network’s native token.
What you’re paying for
Validators (or sequencers on L2s) process your transaction and include it in a block. Gas compensates them for computation and storage. Without fees, the network would be spammed into uselessness.
| Term | Meaning |
|---|---|
| Gas units | How much work your transaction requires |
| Gas price | Price per unit, usually in gwei (1 gwei = 0.000000001 ETH) |
| Total fee | Gas used × gas price |
A simple ETH transfer uses ~21,000 gas. A token swap through a DEX might use 150,000–300,000 gas or more.
Why fees vary so much
Network congestion — when many people transact at once, users bid higher gas prices to get included sooner. Fees can jump 10× during NFT drops or market panic.
Transaction complexity — interacting with smart contracts costs more than sending coins to an address. Multi-step DeFi (approve + swap + deposit) can mean multiple transactions, each with its own fee.
Layer choice — Ethereum mainnet is the most expensive but most settled. L2s (Arbitrum, Base, Optimism) post batches to mainnet and charge a fraction of the cost.
Practical tips
- Keep some native gas token in your wallet — you can’t pay gas in USDC on Ethereum.
- Wallets show an estimated fee before you confirm; expand details to see gas price and limit.
- Failed transactions still cost gas — the network did work even if your swap reverted.
- For small, frequent actions, use an L2. For large, infrequent moves, mainnet security may be worth the fee.
- “Max fee” and “priority fee” (EIP-1559) let you cap what you’ll pay; unused amount is refunded.
A $2 fee on a $50 swap hurts more than the same fee on a $5,000 transfer. Factor gas into position size — especially on mainnet and when yield farming with small balances.