eth_estimateGas - Ethereum

Example code for the eth_estimateGas JSON RPC method. Сomplete guide on how to use eth_estimateGas JSON RPC in GetBlock Web3 documentation.

This method returns an estimate of the gas needed to execute a transaction against the current state. It's typically an overestimate — the node runs the transaction and returns the actual gas cost plus a small buffer. Wallets use this to set the gas field before signing and broadcasting.

Parameters

Parameter	Type	Required	Description
transaction	object	Yes	Transaction call object — same shape as eth_call transaction object
blockParameter	string	No	Block number in hex, or latest, earliest, pending, finalized, safe. Defaults to latest

Request

cURL

curl --location --request POST 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "eth_estimateGas",
    "params": [
        {
            "from": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
            "to": "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2",
            "value": "0xde0b6b3a7640000"
        }
    ],
    "id": "getblock.io"
}'

Axios

example.js

const axios = require('axios');

const response = await axios.post('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/', {
    jsonrpc: '2.0',
    method: 'eth_estimateGas',
    params: [
        {
            "from": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
            "to": "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2",
            "value": "0xde0b6b3a7640000"
        }
    ],
    id: 'getblock.io'
}, {
    headers: { 'Content-Type': 'application/json' }
});

console.log(response.data.result);

Request

example.py

import requests

response = requests.post(
    'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/',
    headers={'Content-Type': 'application/json'},
    json={
        'jsonrpc': '2.0',
        'method': 'eth_estimateGas',
        'params': [
        {
            "from": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
            "to": "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2",
            "value": "0xde0b6b3a7640000"
        }
    ],
        'id': 'getblock.io'
    }
)

print(response.json())

Rust

example.rs

use reqwest::Client;
use serde_json::{json, Value};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = Client::new();
    
    let response = client
        .post("https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/")
        .header("Content-Type", "application/json")
        .json(&json!({
            "jsonrpc": "2.0",
            "method": "eth_estimateGas",
            "params": [
        {
            "from": "0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045",
            "to": "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2",
            "value": "0xde0b6b3a7640000"
        }
    ],
            "id": "getblock.io"
        }))
        .send()
        .await?
        .json::<Value>()
        .await?;
    
    println!("Result: {}", response["result"]);
    Ok(())
}

Response

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0x5208"
}

Response Parameters

Parameter	Type	Description
jsonrpc	string	JSON-RPC protocol version ("2.0")
id	string	Request identifier matching the request
result	string	Hex-encoded gas estimate (typically slightly higher than actual execution cost)

Use Cases

• Pre-Send Gas Estimation: Set the gas field on a transaction before signing to avoid out-of-gas failures

• Transaction Cost Preview: Show users the expected gas cost before they confirm a transaction

• Contract Interaction Sizing: Estimate gas for arbitrary contract calls to display a fee preview in a dApp UI

• Revert Detection: A failing gas estimate typically indicates the transaction would revert on-chain

Error Handling

Error Code	Message	Description
-32602	Invalid params	Transaction object is malformed
3	Execution reverted	The transaction would revert — decode the return data to see the reason
-32000	Execution error	Node failed to estimate gas (usually indicates the transaction can't succeed)

Web3 Integration

Ethers.js

ethers-example.js

import { ethers } from 'ethers';

const provider = new ethers.JsonRpcProvider('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/');

const gasEstimate = await provider.estimateGas({
    from: '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045',
    to: '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2',
    value: ethers.parseEther('1.0'),
});
console.log('Gas estimate:', gasEstimate.toString());

Viem

viem-example.js

import { createPublicClient, http, parseEther } from 'viem';
import { mainnet } from 'viem/chains';

const client = createPublicClient({
    chain: mainnet,
    transport: http('https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/'),
});

const gas = await client.estimateGas({
    account: '0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045',
    to: '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2',
    value: parseEther('1.0'),
});
console.log('Gas estimate:', gas);