How to Pay Gas When Swapping Tokens on Arbitrum

On Arbitrum One, you pay gas for a token swap with ETH held on Arbitrum One, not with the token you are buying or selling. The wallet asks you to approve and sign a transaction; the swap contract then uses that transaction to trade through a liquidity pool. Gas pays for processing that transaction, while any swap fee is a separate charge set by the exchange.

What does the gas charge pay for?

The gas charge covers the work needed to execute your transaction on Arbitrum. The wallet estimates the work, called gas, and the price per unit; together they determine the network fee. Arbitrum also accounts for the transaction data that must be posted to Ethereum, so the total can include both execution and data costs. The wallet shows an estimate before you confirm, and the final charge depends on the transaction and network conditions.

Think of gas as postage for the instruction, not payment for the parcel: it gets the swap processed, but it does not buy the tokens. A swap may also include a trading fee charged by the exchange’s pool. For a fuller account of how a swap interacts with pools and liquidity, see Arbswap’s guide to swaps, liquidity and farming.

Why might a swap need two transactions?

If you have not previously given the exchange permission to use a particular token, you may first need to approve the token contract. That approval is an onchain transaction and uses ETH for gas. The swap itself is another transaction, with its own gas charge. Some exchanges or wallets support a combined approval and swap flow, but check the wallet prompt: if it shows two transactions, each can cost gas.

After approval, the swap transaction tells the exchange contract which tokens to trade and how much. The contract routes the trade through available liquidity and returns the output token if the transaction succeeds. The network fee is not the same as the price impact or slippage, which affect how many tokens the trade returns.

How do you make sure you have enough ETH?

Keep native ETH in your wallet on Arbitrum One before you begin. ETH on Ethereum mainnet is on a different network and cannot pay an Arbitrum One gas charge until bridged over. Wrapped ETH (WETH) is a token used in swaps; it is not the same as native ETH for paying gas.

• Check the wallet’s selected network is Arbitrum One.
• Check that the wallet holds native ETH on that network, beyond the amount you plan to swap.
• Review each wallet prompt for its estimated network fee and whether it is an approval or the swap.
• If you need more ETH on Arbitrum One, bridge some from Ethereum or receive it from another wallet on Arbitrum One.

Leave a little ETH for fees rather than swapping your entire balance. A transaction that fails can still consume gas because the network had to process it. The practical rule is simple: the token pair determines what you trade; native ETH on Arbitrum One covers the network work that makes the trade happen.