eth_estimateGas - Polygon

Example code for the eth_estimateGas json-rpc method. Сomplete guide on how to use eth_estimateGas json-rpc in GetBlock.io Web3 documentation.

The eth_estimateGas method generates and returns an estimate of how much gas is necessary to allow the transaction to complete. The transaction will not be added to the blockchain. The estimate may be significantly more than the amount of gas actually used by the transaction due to a variety of reasons including EVM mechanics and node performance.

Parameters

Parameter	Type	Required	Description
transaction	object	Yes	Transaction call object
blockParameter	string	No	Block number in hex, or "latest", "earliest", "pending" (default: "latest")

Transaction Object

Field	Type	Required	Description
from	string	No	The address the transaction is sent from
to	string	No	The destination address (required for non-contract creation)
gas	string	No	Upper limit of gas for the estimation (hex)
gasPrice	string	No	Gas price in wei (hex)
value	string	No	Value to send in wei (hex)
data	string	No	Contract code or encoded function call

Request

cURL

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": "0x742d35Cc6634C0532925a3b844Bc9e7595f5bEb1",
        "to": "0x7D1AfA7B718fb893dB30A3aBc0Cfc608AaCfeBB0",
        "value": "0x0",
        "data": "0xa9059cbb000000000000000000000000d8dA6BF26964aF9D7eEd9e03E53415D37aA960450000000000000000000000000000000000000000000000056bc75e2d63100000"
    }],
    "id": "getblock.io"
}'

JavaScript (Axios)

estimateGas.js

import axios from 'axios';

const url = 'https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/';

const payload = {
    jsonrpc: '2.0',
    method: 'eth_estimateGas',
    params: [{
        from: '0x742d35Cc6634C0532925a3b844Bc9e7595f5bEb1',
        to: '0x7D1AfA7B718fb893dB30A3aBc0Cfc608AaCfeBB0',
        value: '0x0',
        data: '0xa9059cbb000000000000000000000000d8dA6BF26964aF9D7eEd9e03E53415D37aA960450000000000000000000000000000000000000000000000056bc75e2d63100000'
    }],
    id: 'getblock.io'
};

axios.post(url, payload, {
    headers: { 'Content-Type': 'application/json' }
})
.then(response => {
    const gasEstimate = parseInt(response.data.result, 16);
    console.log('Estimated Gas:', gasEstimate);
})
.catch(error => console.error(error));

Python (requests)

estimate_gas.py

import requests

url = "https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/"

payload = {
    "jsonrpc": "2.0",
    "method": "eth_estimateGas",
    "params": [{
        "from": "0x742d35Cc6634C0532925a3b844Bc9e7595f5bEb1",
        "to": "0x7D1AfA7B718fb893dB30A3aBc0Cfc608AaCfeBB0",
        "value": "0x0",
        "data": "0xa9059cbb000000000000000000000000d8dA6BF26964aF9D7eEd9e03E53415D37aA960450000000000000000000000000000000000000000000000056bc75e2d63100000"
    }],
    "id": "getblock.io"
}

response = requests.post(url, headers={"Content-Type": "application/json"}, json=payload)
result = response.json()
gas_estimate = int(result["result"], 16)
print(f"Estimated Gas: {gas_estimate}")

Rust (reqwest)

main.rs

use reqwest::header;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = reqwest::Client::new();
    
    let response = client
        .post("https://shared.eu-central-1.getblock.io/<ACCESS-TOKEN>/")
        .header(header::CONTENT_TYPE, "application/json")
        .body(r#"{
            "jsonrpc": "2.0",
            "method": "eth_estimateGas",
            "params": [{
                "from": "0x742d35Cc6634C0532925a3b844Bc9e7595f5bEb1",
                "to": "0x7D1AfA7B718fb893dB30A3aBc0Cfc608AaCfeBB0",
                "value": "0x0"
            }],
            "id": "getblock.io"
        }"#)
        .send()
        .await?;
    
    println!("{}", response.text().await?);
    Ok(())
}

Response

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

Response Parameters

Field	Type	Description
jsonrpc	string	JSON-RPC version (2.0)
id	string	Request identifier
result	string	Estimated gas amount in hexadecimal (0x5208 = 21000 for simple transfer)

Use Case

The eth_estimateGas method is essential for:

• Transaction preparation: Determine gas limit before sending transactions

• Cost estimation: Calculate transaction costs for users

• Contract interaction: Estimate gas for complex smart contract calls

• Budget planning: Ensure sufficient funds for transaction execution

• Error prevention: Detect transactions that would fail before sending

Example: Calculate Transaction Cost

import { ethers } from 'ethers';

async function estimateTransactionCost(provider, tx) {
    // Get gas estimate
    const gasEstimate = await provider.estimateGas(tx);
    
    // Get current gas price
    const feeData = await provider.getFeeData();
    
    // Calculate total cost
    const maxCost = gasEstimate * feeData.maxFeePerGas;
    const likelyCost = gasEstimate * feeData.gasPrice;
    
    console.log(`Gas Estimate: ${gasEstimate}`);
    console.log(`Max Cost: ${ethers.formatEther(maxCost)} MATIC`);
    console.log(`Likely Cost: ${ethers.formatEther(likelyCost)} MATIC`);
    
    return { gasEstimate, maxCost, likelyCost };
}

Error Handling

Status Code	Error Message	Cause
403	Forbidden	Missing or invalid ACCESS-TOKEN
-32000	execution reverted	Transaction would fail
-32000	gas required exceeds allowance	Gas limit too low or infinite loop
-32602	Invalid params	Invalid transaction parameters

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: '0x742d35Cc6634C0532925a3b844Bc9e7595f5bEb1',
    to: '0x7D1AfA7B718fb893dB30A3aBc0Cfc608AaCfeBB0',
    value: ethers.parseEther('1.0')
});

console.log('Estimated Gas:', gasEstimate.toString());

Viem

viem-example.js

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

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

const gasEstimate = await client.estimateGas({
    account: '0x742d35Cc6634C0532925a3b844Bc9e7595f5bEb1',
    to: '0x7D1AfA7B718fb893dB30A3aBc0Cfc608AaCfeBB0',
    value: parseEther('1')
});

console.log('Estimated Gas:', gasEstimate);