eth_estimateGas

eth_estimateGas simulates a transaction against current Avalanche C-Chain state and returns the estimated amount of gas it would consume on-chain. Because C-Chain gas is paid in AVAX, this estimate is what you multiply by the gas price to forecast the AVAX cost of a swap, deposit, or contract deployment before you ever sign it. Send the call to https://avalanche.therpc.io/YOUR_API_KEY (chain ID 43114); the node runs the transaction in a sandbox, discards the result, and reports the gas figure as a hex string.

Use cases

• Calculate the gas limit to set on an AVAX transaction before signing it, so it neither under-provisions nor wastes the buffer.
• Estimate the deployment cost of a new contract on the C-Chain (omit to) and convert the gas figure into an AVAX budget.
• Check whether a transaction would succeed without submitting it — a returned estimate means the simulation did not revert.
• Drive live fee estimates in Avalanche wallets and dApps so users see an expected AVAX cost before confirming.

Parameters

Response

Example request

1curl https://avalanche.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 Avalanche playground.

Errors & troubleshooting

Common pitfalls

• The estimate is not a hard guarantee — set the gas limit a little above it (for example ×1.2) so an edge case does not cause an out-of-gas failure that still burns your AVAX.
• If the simulated transaction reverts, you get an error (code 3 or -32000), not a gas number — handle that path instead of expecting a value.
• Gas usage can shift between estimation and execution when contract state changes in between; on the fast ~1–2s C-Chain, several blocks can pass before your transaction is included, so re-estimate if the gap grows.

Supported networks

• Mainnet — Chain ID: 43114
• Fuji

See also

• eth_call
• eth_sendRawTransaction
• eth_gasPrice
• eth_feeHistory

1curl https://avalanche.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]}'