I'm creating a smart contract that does the following:

  • Checks that a userID parameter is included as data field OR
  • that the last 4 zeros of the amount being sent is not equal to zero (i.e, 0.1230000000000001234 is OK. 0.1230000000000000000 or 0.1230000000000001004 are not OK)


 function accept() public payable {
        require(msg.value == 0.00000000000000XXXX);
        // X means non zero

If neither of the above rules are satisfied the contract "rejects" the transaction. If either of the above is satisfied the total amount is forwarded to a EOA (assume to an address with a non zero balance)

I'm trying to calculate the estimated gas costs in each of the following scenarios:

When the Transaction Succeeds:

In this case, the gas costs can be calculated as follows:

  • 21,000 base gas cost

  • the fee to invoke the smart contract which evaluates whether userID/wei marker are present (which I believe is < 500 gwei according to this document)

  • the fee for each byte of data that is included in the transaction (such as a userID) which is approx. 68 gwei per byte (we could assume max of 1 byte for the userID)

  • the fee for the smart contract to transfer/forward funds to the EOA for invoking send or transfer or call.value().gas function. According to this thread the fee is fixed at 2,300

  • In addition, as the creator of the contract I would pay a one time fee for deployment

So 21,000 + (approx.) 500 + 68 + 2,300 = 28,068.

When the Transaction Fails:

If neither of the two conditions are satisfied, the transaction would be rejected by the contract (so the funds would not be forwarded) but the sender would still need to pay:

  • a fee for invoking above function (approx. 500)

  • (??) the base fee of 21,000?

  • In addition, as the creator of the contract I would pay a one time fee for deployment

Does the sender still pay 21,000 base fee when the transaction is aborted?

Do I have the correct approach in calculating the fee in each of the above scenarios?


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