eth_estimateGas

Estimates the gas necessary to execute a transaction on Moonriver.

Why Moonriver? Build on the Moonbeam canary network on Kusama for real-world testing of EVM dApps with Moonbeam code ships here first, full EVM compatibility on Kusama, 80% fee burn mechanism, and XCM cross-chain messaging.

Use Cases

The eth_estimateGas method is essential for:

• Transaction preparation - Set appropriate gas limits
• Cost estimation - Calculate transaction costs before sending
• Error detection - Identify reverts before spending gas
• DeFi operations - Estimate costs for production-grade dApp testing, early feature deployment, and Kusama-based EVM applications

Parameters

Parameter	Type	Required	Description
from	DATA	No	Sender address
to	DATA	No	Recipient address
gas	QUANTITY	No	Gas limit
gasPrice	QUANTITY	No	Gas price
value	QUANTITY	No	Value in wei
data	DATA	No	Transaction data

Request

{
  "jsonrpc": "2.0",
  "method": "eth_estimateGas",
  "params": [{
    "from": "5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY",
    "to": "5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY",
    "value": "0x1"
  }],
  "id": 1
}

Returns

Type	Description
QUANTITY	Estimated gas amount in hexadecimal

Response

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x5208"
}

Note: 0x5208 = 21000 gas (standard ETH transfer)

Code Examples

cURL

curl -X POST  \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_estimateGas",
    "params": [{
      "from": "5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY",
      "to": "5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY",
      "value": "0x1"
    }],
    "id": 1
  }'

JavaScript

import { JsonRpcProvider, parseEther } from 'ethers';

const provider = new JsonRpcProvider('');

// Estimate simple transfer
async function estimateTransfer(to, value) {
  const gasEstimate = await provider.estimateGas({
    to: to,
    value: parseEther(value)
  });

  console.log('Estimated gas:', gasEstimate.toString());
  return gasEstimate;
}

// Estimate contract call
async function estimateContractCall(contract, method, args) {
  const gasEstimate = await contract[method].estimateGas(...args);
  console.log('Estimated gas:', gasEstimate.toString());

  // Add 20% buffer for safety
  return gasEstimate * 120n / 100n;
}

Python

from web3 import Web3

w3 = Web3(Web3.HTTPProvider(''))

def estimate_transfer(to, value_in_ether):
    gas_estimate = w3.eth.estimate_gas({
        'to': to,
        'value': w3.to_wei(value_in_ether, 'ether')
    })

    print(f'Estimated gas: {gas_estimate}')
    return gas_estimate

def estimate_contract_call(contract, method, args):
    func = getattr(contract.functions, method)
    gas_estimate = func(*args).estimate_gas()

    # Add 20% buffer
    return int(gas_estimate * 1.2)

# Estimate simple transfer
gas = estimate_transfer('5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY', 0.1)

Go

package main

import (
    "context"
    "fmt"
    "log"
    "math/big"

    "github.com/ethereum/go-ethereum"
    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/ethclient"
)

func main() {
    client, err := ethclient.Dial("")
    if err != nil {
        log.Fatal(err)
    }

    toAddress := common.HexToAddress("5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY")
    msg := ethereum.CallMsg{
        To:    &toAddress,
        Value: big.NewInt(1000000000000000000),
    }

    gasLimit, err := client.EstimateGas(context.Background(), msg)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Printf("Estimated gas: %d\n", gasLimit)
}

Error Handling

Error Code	Message	Description
-32000	Execution reverted	Transaction would fail
-32602	Invalid params	Invalid transaction parameters

Tip: If estimation fails, the transaction would likely revert if sent.

Related Methods

• eth_gasPrice - Get current gas price
• eth_sendRawTransaction - Send transaction