[Ethereum] How to calculate the gas fee of a swap on Uniswap

gasgas-estimategas-priceuniswap

According to gas tracker on Etherscan the average gas price is 212 gwei and the average Uniswap swap estimate is $70.26 which implies that the gas fee is around 201101.
To my knowledge swap gas fee is 21000 or so. What other operations are associated with a Uniswap swap that burn the extra gas?

Best Answer

To my knowledge swap gas fee is 21000 or so

A transfer between two EOAs (i.e. normal wallet accounts) is 21,000 gas.

As soon as you include smart contracts in the equation the gas cost increases: each opcode associated with each step in the execution of a smart contract incurs a cost. (As outlined in Appendix G of the Yellow Paper.)

Without actually digging into the opcodes associated with a Uniswap (v2) swap operation, just looking at an example transaction gives an idea that there's a lot going on when swapping from token A -> token B.

Generally it's a 3-part process (this is for the swapExactTokensForTokens() path):

User transfers token A to Uniswap where it's converted to wrapped ETH (WETH)
The WETH is swapped for token B
Token B is transferred to the user

However, if you look a bit deeper at the example above, this 3-part process actually involves 13 internal transactions (i.e. messages between contracts) - there's a lot going on.

(If you want to dig deeper, then the v2 contracts are here: https://github.com/Uniswap/uniswap-v2-core)

There is no minimum for gas price

You can set a transaction with 10wei as gas price if you want.

The problem is most miners won't include transactions below it. You can see here http://ethgasstation.info/ the minimun gwei each miners pool ask for. It seems right now the minimun is 1gwei and it will take 1.5 minutes.

However with tools like MyEtherWallet or Metamask the minimun is indeed 2gwei because actually it is "the cheapest" miners accept.

But in the future we might see this reduced again but for this more miners will have to accept transactions below it.

If you want to set manually your gas price I advice you to use a client like geth

eth.sendTransaction({
 from: '0x036a03fc47084741f83938296a1c8ef67f6e34fa',
 to: '0xa8ade7feab1ece71446bed25fa0cf6745c19c3d5', 
 value: web3.toWei(1, "ether"),
 gas: 100000,
 gasPrice: /* gasPrice in wei */ 
})

Remember one gwei is equal to 1billion wei

[Ethereum] Price of 1 gas in dollars

1 Ether = 10^9 Gwei

i.e. Price of 1 Gwei = Price of 1 Ether / 10^9

Given Price of 1 Ether = 520 dollars

Price of 1 Gwei = 5.2 * 10^-7 dollars or 0.000052 cents.

Thus if 1 gas = 2 Gwei, then 1 gas = 0.000104 cents.

Not sure why your calculation involved a square root.

Best Answer

Related Solutions

[Ethereum] Can gas price be fixed under 2 gwei

There is no minimum for gas price

[Ethereum] Price of 1 gas in dollars

Related Topic