Estimate gas price does input amount matter ?

[Sharkoon1]

Hello,

I would like to calculate the amount of gas used before sending multiple transactions. I.e using

const estimation = await erc20.estimateGas.transfer(recipient, 100);

My question: does the amount and reicipient parameter matter or is the gas price of a certain contract function always the same? I need to calculate the gas price before I know the amount.

This is probably a general "contract"/"gas price" issue and not related to ether, well maybe it is, but would be thankful for a good answer anyways.

Thank you guys!

[ricmoo]

These are different idea. There is no longer a concept of gasPrice. The estimateGas returns the gasLimit, which is how many units of gas to allow the transaction to consume.

Historically a gasPrice was how much to pay per unit of gas (in Wei); there is a new concept of effectiveGasPrice, which is decided in-protocol based on two new properties, maxFeePerGas and maxPriorityFeePerGas. You generally do not need to worry about these, as the network provides quite suitable values for this. So price is probably not what you are interested in (other than if you have a UI which wishes to show the user an approximate final cost in ether; in which case you multiply this value by the gasLimit).

For gasLimit (which is what estimateGas computes), it will vary depending on what a contract does. Every operation in Ethereum has some associated cost so it depends on the operations your transaction performs.

Does that make sense?

[Sharkoon1]

That totaly makes sense, but what I actually want to find out I guess is the transaction fees.

What I read is that the transaction fee is calculated by:

(gas limit x gas price) = transaction fee

Where you mentioned gas price is basically the new concept effectiveGasPrice.

To estimate the transaction fees, would I do it like this?

let gasPrice = await provider.getGasPrice()
let  gasLimit = await erc20.estimateGas.transfer(recipient, 100);

let transactionFee = gasPrice * gasLimit, 

And back to my question, you mentioned: "Every operation in Ethereum has some associated cost so it depends on the operations your transaction performs.". I was aware of this.
If the contract perfoms the same action irrelevant of the input amount, the gas limit should be for all transactions the same ?

[ricmoo]

Do not use getGasPrice, it is deprecated and if you use it for any purpose in EIP-1559, you will pay approximately twice the fees you need to.

What you can compute for a UI is “maximum fee”, while the expected fee is lower (I personally find it is around 60% of the maximum fee).

You can use (await provider.getFeeData()).maxFeePerGas.mul(gasLimit) to compute the maximum fee in wei. So, close to what you have, but use getFeeData instead of getGasPrice.

As for the gasLimit, it is definitely not always the same. For example, it costs more to change a zero to a non-zero than it costs to change a non-zero to another non-zero than it costs to change non-zero to a zero in storage, so in the case of an ERC-20 contract, it will cost more to send tokens to a user that has no tokens (changing their 0 to a non-zero) than to an a user that already has tokens (non-zero to non-zero).

A single transfer may execute 1000’s of operations, each with very carefully balanced costs to the network. The goal is to make sure a transactions costs match the node resources it consumes; a transaction that hits the disk drive twice as much as another transaction should cost about twice as much. A transaction that performs twice as much computation should cost twice as much. A transaction that increases the state trie by twice as much should cost twice as much. And so on. The estimateGas is your friend, since it does all the maths for you; but you likely cannot use the same value across all transfers, for example.

That said, you specify a gasLimit, which can be higher than the gas that will be used (you are refunded any unused gas), so I would usually pick a number that seems like a good worst-case gasLimit and hard code that into the code. You can use estimate gas and just add a buffer (like 10-20%) to get a rough idea of worst-case for a given call.

It’s a complex topic, so I hope that helps. :)

[Sharkoon1]

Hi there again, @ricmoo I've just implemented this and stumbled upon a problem.

Somehow in BSC maxFeePerGas is null on getFeeData(). Is it because bsc doesn't use EIP-1559 yet and if so do I need to use gasPrice here ? On the ETH network maxFeePerGas is set.

[edumudu]

@Sharkoon1 yes, bsc still doesn't use EIP-1559, in the docs of the method getFeeData I found this

For legacy transactions and networks which do not support EIP-1559, the gasPrice should be used.

[wb-ts]

Mostly , we use gas fee 21,000 as default. And Also Estimating Gas Lee for transaction is also important.

So we can refer this article for estimate gas fee.

[samyan]

The article is not exist. Can you refresh the link pls?

[efecarranza]

@ricmoo Hey Richard, getFeeData() when using the Polygon network returns a very low number for maxFeePerGas in Gwei (1.5) when gasPrice is 30.
If I don't specify the gasPrice on my transaction, I get transaction underpriced. Do you support eth_feeHistory so I could calculate it based on that?
Any plans on updating maxFeePerGas for the Polygon network?

Thank you