Gas fees on Ethereum and layer 2s, explained
Base fee, priority fee, gas limits, and why the same swap costs cents on a layer 2 and dollars on Ethereum, with tips for paying less and not getting stuck.
Updated 14 Sept 2026 · Intermediate · 3 min read
In short
- Gas measures computation. You pay gas used × (base fee + priority fee), in the chain’s native coin.
- Since EIP-1559 the base fee is set by the protocol and burned; the priority fee is a tip for the block producer.
- Layer 2s such as Arbitrum, OP Mainnet and Base add a fee for posting their data to Ethereum, which became much cheaper in 2024.
Gas, gwei and what you pay
Every operation on an EVM chain costs a fixed amount of gas. A plain ETH transfer uses exactly 21,000 gas; a token transfer typically uses tens of thousands; a swap on a decentralised exchange often 100,000 or more. Gas prices are quoted in gwei, one billionth of an ether.
fee = gas used × (base fee + priority fee)Base fee and priority fee
Since the London upgrade in August 2021 (EIP-1559), each block has a base fee set by the protocol. It rises when blocks are more than half full and falls when they are less, by at most 12.5% per block, so it tracks demand smoothly. The base fee is burned. On top of it you add a priority fee: A tip for the validator that includes your transaction.
Wallets also ask for a max fee: the most you are willing to pay per unit of gas. You pay only the actual base fee plus your tip; the difference is never charged. A generous max fee protects you from the base fee rising while your transaction waits.
Gas limits and failed transactions
The gas limit is the most gas your transaction may use, and wallets estimate it for you. If execution runs out of gas or reverts, the transaction fails, and the gas it used is still charged, because the network did the work. Failed swaps in volatile moments are a common way to pay a fee for nothing; a realistic slippage setting helps.
Layer 2s: why they are cheaper
Rollups such as Arbitrum One, OP Mainnet and Base execute transactions themselves and post compressed transaction data to Ethereum, which secures them. Their fee has two parts: the layer 2 execution fee, usually tiny, and a data fee for the share of Ethereum space the transaction’s data uses. The Dencun upgrade in March 2024 (EIP-4844) gave rollups a separate, cheaper kind of space (“blobs”) and layer 2 fees fell sharply.
Polygon PoS and BNB Smart Chain are not Ethereum rollups: they have their own validators and gas tokens (POL and BNB). Their fees are usually low, with different security trade-offs.
Paying less, and not getting stuck
- Send when the base fee is low: demand varies through the day and week.
- When blocks are not full, a small priority fee is enough.
- Do the same action on a layer 2 when the asset and the app are available there.
- A transaction stuck with too low a fee can be replaced: send a new one with the same nonce and a higher fee (“speed up” in most wallets), or a zero-value transfer to yourself with the same nonce to cancel it.