Please let me know to delete the question if it's already been asked.

I was told (by a colleague of mine) that adding more external function to a smart contract increases its gas. I tested (on remix and metamask) and it's true, for example when my contract has only one external function and one internal function the total gas is: 89941. But if I change the internal one to external function, (so two external functions) then the gas would be 99943.

Question: Why does a contract having more external function require more gas (when it's deployed)? Is it due to memory/storage allocation?

  • Is this about deploying the contract? Mar 15, 2018 at 19:32
  • @cleanunicorn yes that's right. I've edited my question accordingly.
    – Aydin
    Mar 15, 2018 at 20:09

1 Answer 1


For each public or external function the contract has to have code that accept a calls to the function. For internal or private function no code is generated (you cannot call to them from other contracts).

If you use external in a function it will force the function to always use a external call when you use the function (ie CALL opcode). Usually the solidity compiler will make function calls to be jumps (ie JMP opcode).

  • Thank you very much for the answer. Am I right that, because for an external function some extra code is required and this occupies some storage, the external functions impose some costs on the contract?
    – Aydin
    Mar 16, 2018 at 10:03
  • Yes, an external and public functions requires some extra code for the contract to accepts calls to them.
    – Ismael
    Mar 16, 2018 at 17:50

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