Is a Wallet/Signer required when estimating gas?

[Mantas-M]

Hello, was doing some research and it seems like viem requires you to have an account or a wallet on the publicClient for gas estimations, and it fails the call if it's not present saying the gas of the account is insufficient.

The total cost (gas * gas fee + value) of executing this transaction exceeds the balance of the account

Even though I only want an estimate and not to execute anything. Though I've switched it to a RPC call and everything seems to work.

RPC

    const response = await (
      await fetch(Config.rpc_url, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({
          jsonrpc: '2.0',
          id: 1,
          method: 'eth_estimateGas',
          params: [{ from, to, value: toHex(amount), data }, 'latest']
        })
      })
    ).json()

    return BigInt(response.result as string)

Viem

     return client.estimateGas({
       account: from,
       to,
       value: amount,
       data,
       blockTag: 'latest'
     })

Is there some workaround or am I missing something with the viem call?

[wesleysmyth]

No, you do not need a wallet or signer to estimate gas. estimateGas is a read-only RPC call (eth_estimateGas) that simulates the transaction without broadcasting it. A publicClient is sufficient.

The key detail: you need to pass the account (address) in the call params so the node knows which address to simulate the transaction from:

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

const client = createPublicClient({
  chain: mainnet,
  transport: http(),
});

// Estimate gas WITHOUT a wallet — just pass the sender address
const gasEstimate = await client.estimateGas({
  account: '0xYourAddressHere', // just an address string, not a signer
  to: '0xRecipientAddress',
  value: parseEther('0.1'),
});

console.log('Estimated gas:', gasEstimate); // bigint

For contract calls

import { parseAbi } from 'viem';

const abi = parseAbi(['function transfer(address to, uint256 amount) returns (bool)']);

const gas = await client.estimateContractGas({
  address: '0xTokenContractAddress',
  abi,
  functionName: 'transfer',
  args: ['0xRecipient', 1000000n],
  account: '0xYourAddressHere', // address string is fine
});

When you DO need a wallet

Only if you want viem to automatically populate the account field from the connected wallet:

import { createWalletClient, custom } from 'viem';

const walletClient = createWalletClient({
  chain: mainnet,
  transport: custom(window.ethereum!),
  account: '0x...', // or from wallet
});

// Now `account` is implicit — pulled from walletClient
const gas = await walletClient.estimateGas({
  to: '0xRecipient',
  value: parseEther('0.1'),
  // account is auto-populated
});

TL;DR: publicClient.estimateGas() works fine. Just pass account: '0x...' as a plain address string in the params.

[HereForTheTechNFT]

You don't need a wallet, but the error depends on what kind of account you pass, because that changes what viem sends to the node. I logged the eth_estimateGas request viem builds (2.57.5, same result with 2.43.0):

• account as a plain address string: viem sends { from, to, value }, exactly like your raw RPC call.
• account as a local account (privateKeyToAccount, mnemonicToAccount, …), or a client created with such an account: viem prepares the transaction first and adds maxFeePerGas, maxPriorityFeePerGas and nonce.

With fee fields in the request, the node checks that the balance covers gas * maxFeePerGas + value and fails with "insufficient funds", which viem reports as the error you saw. Without fee fields, geth-style nodes treat the gas price as zero for the estimate, so only value has to be covered. That's why your raw call works.

So if from is an account object, pass its address, or skip the preparation step:

await client.estimateGas({ account: from.address, to, value: amount, data })
// or
await client.estimateGas({ account: from, to, value: amount, data, prepare: false })

Both send the same request as your fetch version.