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. Note that the estimate may be significantly more than the amount of gas actually used by the transaction, for a variety of reasons including EVM mechanics and node performance.

Method Limitations

To prevent abusive of the API, the gas parameter to eth_estimateGas and eth_call are capped at 10x (1000%) the current block gas limit. You can recreate this behavior in your local test environment (ganache, besu, geth, or other client) via the rpc.gascap command-line option.

REQUEST

POST https://rbc-rpc.com

HEADER

Content-Type: application/json

REQUEST PAYLOAD

• TRANSACTION CALL OBJECT [required]

  • from: [optional] 20 Bytes - The address the transaction is sent from.

  • to: 20 Bytes - The address the transaction is directed to.

  • gas: [optional] Integer of the gas provided for the transaction execution. eth_estimateGas consumes zero gas, but this parameter may be needed by some executions.

  • gasPrice: [optional] Integer of the gasPrice used for each paid gas

  • value: [optional] Integer of the value sent with this transaction

  • data: [optional] Hash of the method signature and encoded parameters. For details see Ethereum Contract ABI

If no gas limit is specified geth uses the block gas limit from the pending block as an upper bound. As a result the returned estimate might not be enough to executed the call/transaction when the amount of gas is higher than the pending block gas limit.

EXAMPLE

## JSON-RPC over HTTPS POST
curl https://rbc-rpc.com \
    -X POST \
    -H "Content-Type: application/json" \
    -d '{"jsonrpc":"2.0","method":"eth_estimateGas","params": [{"from": "0xb60e8dd61c5d32be8058bb8eb970870f07233155","to": "0xd46e8dd67c5d32be8058bb8eb970870f07244567","gas": "0x76c0","gasPrice": "0x9184e72a000","value": "0x9184e72a","data": "0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675"}],"id":1}'

## JSON-RPC over WSS
wscat -c ws://rbc-rpc.com
>{"jsonrpc":"2.0","method":"eth_estimateGas","params": [{"from": "0xb60e8dd61c5d32be8058bb8eb970870f07233155","to": "0xd46e8dd67c5d32be8058bb8eb970870f07244567","gas": "0x76c0","gasPrice": "0x9184e72a000","value": "0x9184e72a","data": "0xd46e8dd67c5d32be8d46e8dd67c5d32be8058bb8eb970870f072445675058bb8eb970870f072445675"}],"id":1}

RESPONSE

RESULT FIELDS

GAS USED - the amount of gas used.

BODY

{
    "jsonrpc": "2.0",
    "id": 1,
    "result": "0x5cec"
}

On Mainnet, Rinkeby, Ropsten and Goerli, if this call causes the EVM to execute a REVERT operation, an error response of the following form is returned, with the revert reason pre-decoded as a string (not yet supported on Kovan):

{
    "jsonrpc": "2.0",
    "id": 1,
    "error": {
        "code": 3,
        "message": "execution reverted: Dai/insufficient-balance",
        "data": "0x08c379a0000000000000000000000000000000000000000000000000000000000000002000000000000000000000000000000000000000000000000000000000000000184461692f696e73756666696369656e742d62616c616e63650000000000000000"
    }
}