On this page

eth_estimateGas

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.

Parameters

Index	Type	Description
0	`object`	Transaction object
1	`string`	Block number or tag (optional)

Transaction Object

Field	Type	Required	Description
`from`	`string`	No	Sender address
`to`	`string`	No	Recipient address
`data`	`string`	No	Contract call data
`value`	`string`	No	Value in wei (hex)
`gas`	`string`	No	Gas limit (hex)
`gasPrice`	`string`	No	Gas price (hex)

Returns

string - The estimated gas amount (hex)

Example

Estimate ETH Transfer


const gasEstimate = await window.$onekey.ethereum.request({
  method: 'eth_estimateGas',
  params: [{
    from: '0xYourAddress...',
    to: '0xRecipientAddress...',
    value: '0xDE0B6B3A7640000' // 1 ETH
  }]
})
 
console.log('Estimated gas:', parseInt(gasEstimate, 16))
// Simple ETH transfer: ~21000

Estimate Contract Call


const gasEstimate = await window.$onekey.ethereum.request({
  method: 'eth_estimateGas',
  params: [{
    from: '0xYourAddress...',
    to: '0xContractAddress...',
    data: '0xa9059cbb...' // transfer(address,uint256)
  }]
})
 
console.log('Estimated gas:', parseInt(gasEstimate, 16))

Add Safety Buffer


async function estimateGasWithBuffer(tx, bufferPercent = 20) {
  const estimate = await window.$onekey.ethereum.request({
    method: 'eth_estimateGas',
    params: [tx]
  })
 
  const gas = parseInt(estimate, 16)
  const bufferedGas = Math.ceil(gas * (1 + bufferPercent / 100))
 
  return '0x' + bufferedGas.toString(16)
}
 
const safeGasLimit = await estimateGasWithBuffer({
  from: accounts[0],
  to: contractAddress,
  data: encodedData
})

Errors

Code	Message	Description
-32000	Execution reverted	Transaction would fail
-32000	Insufficient funds	Not enough balance
-32602	Invalid params	Invalid transaction parameters

Notes

The estimate may not be exact; transactions can use more or less gas
Add a buffer (10-20%) to the estimate for safety
If estimation fails, the transaction would likely fail too
Estimation considers the current blockchain state