estimate gas for transaction
Note that the interactive example in this page will not work, due to the fact that eth_estimateGas is used to modify the state of the blockchain, it is not possible to duplicate the same request.
Description
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.
Parameters
See eth_call parameters, except that all properties are optional. 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.
Returns
QUANTITY - the amount of gas used.