eth_estimateGas - Base

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

The eth_estimateGas method generates and returns an estimate of how much gas is necessary to allow a transaction to complete. This estimate may be significantly more than the actual gas used due to EVM mechanics and node performance variations.

Parameters

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

Transaction Object

Field	Type	Required	Description
from	string	No	20-byte sender address
to	string	No	20-byte recipient address (optional for contract creation)
gas	string	No	Gas limit (hex)
gasPrice	string	No	Gas price in wei (hex)
value	string	No	Value to send in wei (hex)
data	string	No	Transaction data (hex)

Request

cURL

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "eth_estimateGas",
    "params": [{
        "from": "0x742d35Cc6634C0532925a3b844Bc9e7595f5bE21",
        "to": "0x4200000000000000000000000000000000000006",
        "data": "0xa9059cbb0000000000000000000000001234567890123456789012345678901234567890000000000000000000000000000000000000000000000000016345785d8a0000"
    }],
    "id": "getblock.io"
}'

Axios (JavaScript)

Requests (Python)

Rust

Response

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": "0xc350"
}

Response Parameters

Parameter	Type	Description
jsonrpc	string	JSON-RPC protocol version ("2.0")
id	string	Request identifier matching the request
result	string	Estimated gas required in hex

Use Cases

• Gas Limit Setting: Determine appropriate gas limit for transactions

• Cost Estimation: Calculate transaction costs before sending

• UI Display: Show estimated fees to users before confirmation

• Transaction Validation: Pre-validate transactions will succeed

• Batch Processing: Estimate gas for multiple operations

Error Handling

Error Code	Message	Description
-32602	Invalid params	Invalid transaction object
-32603	Internal error	Estimation failed
3	Execution reverted	Transaction would revert
-32000	Execution error	Insufficient balance or other failure

Web3 Integration

Ethers.js

ethers-example.js

const { ethers } = require('ethers');

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

async function estimateGas(tx) {
    try {
        const gasEstimate = await provider.estimateGas(tx);
        console.log('Gas Estimate:', gasEstimate.toString());
        
        // Add 20% buffer for safety
        const gasLimit = gasEstimate * 120n / 100n;
        console.log('Gas Limit (with buffer):', gasLimit.toString());
        
        return gasLimit;
    } catch (error) {
        console.error('Estimation failed:', error.message);
        throw error;
    }
}

// ETH transfer
estimateGas({
    from: '0x742d35Cc6634C0532925a3b844Bc9e7595f5bE21',
    to: '0x1234567890123456789012345678901234567890',
    value: ethers.parseEther('0.1')
});

// Contract call
async function estimateContractGas(contractAddress, abi, functionName, args, from) {
    const contract = new ethers.Contract(contractAddress, abi, provider);
    
    const gasEstimate = await contract[functionName].estimateGas(...args, { from });
    console.log('Contract Gas Estimate:', gasEstimate.toString());
    
    return gasEstimate;
}

Viem