How Much Native Gas Does a Cross-Chain Swap Need?

There is no fixed amount of native gas for a cross-chain swap; you need enough of the sending chain’s native coin to submit the transaction. The required fee depends on the chain, network conditions, and the transaction the route asks your wallet to make. Ethereum.org explains that Ethereum gas fees are paid in ETH, while Solana’s documentation says Solana transaction fees are paid in SOL. A fuller guide to choosing a thor swap route can help explain what happens after you send.

Which chain’s native coin pays the first fee?

The sending chain’s native coin pays for the transaction that moves your asset into the swap route. Your wallet should show this network fee before you confirm. For example, a token on Ethereum still needs ETH for its transaction fee; Solana’s docs likewise say transactions involving other tokens still require SOL for fees. Holding the token you plan to swap does not necessarily cover this cost.

The fee is not a fixed “swap charge.” On Ethereum, the fee depends on gas used and the price per unit of gas, according to Ethereum.org. Solana’s fee documentation describes a base fee and an optional priority fee, which can raise the cost if you choose to pay for faster scheduling. Other chains use their own fee rules.

Do you also need gas on the destination chain?

Sometimes, but it depends on what the route does and what you want to do next. If the swap delivers tokens to your own wallet, you may need the destination chain’s native coin later to send or trade them. That future fee is separate from the fee to start the swap.

Some routes cover the transaction that delivers the swap output and account for its cost in the quote. THORChain’s developer documentation, for example, says users pay the inbound network fee themselves, while the outbound fee for delivery is charged from the swap output. That does not mean every cross-chain service handles delivery the same way. Check the route’s fee breakdown and whether the output arrives ready for another transaction.

How can you estimate the amount before swapping?

Use the wallet estimate and a fresh route quote, since both the fee and route can vary. THORChain’s documentation says its swap quote calculates and shows fees; Ethereum.org and Solana’s docs describe how network fees are determined on those chains. Treat the wallet’s displayed fee as the estimate for the transaction you are about to sign.

• Check that the wallet is connected to the intended sending network.
• Keep enough of that network’s native coin for the displayed fee.
• Read the quote to see whether destination delivery costs come from the output.
• If you will spend the received tokens again, keep destination-chain gas for that later transaction.

For a THORChain swap, its documentation also says a failed or refunded swap may incur a source-chain outbound fee. This is a reason to check the quote and leave room in the amount you send, especially for a small swap. The practical rule is simple: fund the sending chain to submit the swap, then check whether the route’s output and your next move require anything more.