What is Gas?
By definition, gas is a unit that measures the amount of computational effort that it will take to execute certain operations on the Ethereum blockchain. The operations include sending tokens, deploying a smart contract, interacting with a contract, sending some ETH, launching an ICO, or anything else on the blockchain. Gas is needed to power the Ethereum Ecosystem, just like fuel is needed to power a car.
What is Gas Price?
As I have mentioned earlier, we need to use gas
Gas price is the amount of Ether you need to pay per unit of gas. It is measured in Gwei (1Gwei=0.0000000001 ETH). Its value is determined by the miners, who can refuse to process the transaction with less than a certain gas price. The transaction fee is paid to the successful miner as a form of incentive that motivates the miners to maintain the nodes. Therefore, they have the controlling power over the gas price. We must have enough ether in our wallet to pay for the gas fees.
The transaction fee is calculated using the following formula
Transaction fee= Gas unit used x Gas price
For example, for a certain transaction,
gas unit used=103631
Gas price= 1Gwei or 0.000000001 Eth
So transaction fee= 103631×0.000000001 Eth=0.000103631 Eth
You can see the actual output in a smart contract deployment on Etherescan, as shown in the figure below:
In addition, you can “bribe” the miners to do your work first by paying more gas fees. In this way, you can jump to the front of the queue so that your transaction can be processed first. Even if the transaction fails, you still need to pay for the transaction fee because the miners must validate and execute your transaction.
The Gas Limit is an estimation of the total amount of work to perform a transaction. It is not easy to compute the gas limit. Fortunately, there are many apps that set the limit for us. Typically, 21,000 Gas will satisfy most transactions. However, for more complex transactions such as sending ETH to an ICO smart contract, the gas limit will be much higher. The reason is such a transaction requires much more computational power.
If you set the limit is too low, your transaction may take too long to process and even fail. As a result, you will lose ETH for nothing. On the other hand, if your transaction was completed before reaching the gas limit, you get back the balance ETH. The Gas Limit protects you from spending unlimited ETH, just like what banks set your credit card limit so that you will not overspend.