eth_estimateGas

eth_estimateGas simulates a transaction against current OP Mainnet state and returns the estimated amount of L2 execution gas required to run it, priced in ETH. On this OP Stack rollup the figure it returns covers L2 execution only — the separate L1 data fee for posting the transaction to Ethereum is added at submission time and is not part of this estimate. Send the request to https://optimism.therpc.io/YOUR_API_KEY (chain ID 10, 0xa) to size a gas limit before signing.

Use cases

• Calculate the gas limit to set on an OP Mainnet transaction before signing it.
• Estimate the L2 execution cost of deploying a new contract by omitting to and passing the deploy bytecode as data.
• Check whether a transaction would succeed on chain 10 without actually submitting it — a revert during estimation means it would fail on-chain.
• Drive fee estimates in OP Mainnet wallets and dApps such as Velodrome or Synthetix front ends.

Parameters

Response

Example request

1curl https://optimism.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5    "jsonrpc": "2.0",
6    "method": "eth_estimateGas",
7    "params": [
8        {
9          "to": "0x0000000000000000000000000000000000000000",
10          "data": "0x"
11        },
12        "latest"
13      ],
14    "id": 1
15  }'

Try it live in the Optimism playground.

Errors & troubleshooting

Common pitfalls

• The estimate is not a hard guarantee — pad it (e.g. ×1.2) when setting the gas limit so OP Mainnet's ~2s state changes don't push you into an edge-case out-of-gas failure.
• A simulated revert returns an error (code 3 or -32000), not a gas number — handle that path and surface the revert reason instead of assuming success.
• The returned figure is L2 execution gas only; budget separately for OP Mainnet's L1 data fee when estimating the total ETH a user will pay.

Supported networks

• Mainnet — Chain ID: 10
• Sepolia — Chain ID: 11155420

See also

• eth_call
• eth_sendRawTransaction
• eth_gasPrice
• eth_feeHistory

1curl https://optimism.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H 'Content-Type: application/json' \
4  -d '{"jsonrpc":"2.0","id":1,"method":"eth_estimateGas","params":[{"to":"0x0000000000000000000000000000000000000000","data":"0x"},"",null]}'