What Is Gas?

Ethereum is the network, also known as the blockchain. Ether (ETH) is the fuel for that network. When you send tokens, interact with a contract, send ETH, or do anything else on the blockchain, you must pay for that computation. That payment is calculated in gas, and gas is paid in ETH.

You are paying for the computation, regardless of whether your transaction succeeds or fails. Even if it fails, the miners must validate and execute your transaction (compute) and therefore you must pay for that computation just like you would pay for a successful transaction.

Any time you send a transaction on Ethereum you must pay a transaction fee. This fee is known as "gas" and is paid with Ether.

You can see your transaction fee (Gas limit × Gas price) in ETH & USD values when you search for your transaction on Etherscan.io. This is not a transaction fee that MyCrypto, or any other service provider, receives. This fee is paid to miners for mining transactions, putting them into blocks, and securing the blockchain.

The amount you must pay to send a transaction increases as a transaction gets more complex and as the Ethereum network gets busier. For example, simply sending Ether to someone requires the smallest fee, and interacting with complex smart contracts costs more. Similarly, it used to be that the network was rarely full of transactions, but today it's almost always busy.

Does Bitcoin Have Gas?

Bitcoin and Ethereum are similar in that both require a fee to be paid in the block and with native coin.

• To transact on the Bitcoin blockchain, an amount of Bitcoin is required as a fee.
• To transact on the Ethereum blockchain, an amount of Ether is required as a fee.

But while Bitcoin requires a transaction fee that is paid in its native coin, it isn't called gas, and the amount needed to send is not calculated in the same way. What determines the amount I must pay as a transaction fee? There are two main factors for determining the price of a transaction: gas limit and gas price.

The gas limit is the maximum amount of computational resources that can be utilized to complete the transaction, and is usually estimated fairly accurately. Sometimes you’ll actually use less than estimated, in which case the leftover amount will be refunded.

The least expensive transaction on the Ethereum blockchain is the simple function of sending ETH from one externally owned account (an “EOA”) to another; this would have a gas limit of 21000.

The more complicated a transaction is and the more functions it involves, the more gas that transaction will require. Some highly complicated transactions can use millions of units of gas.

The gas price is commonly denoted in gwei and is on a scale that starts from 0 and goes to 500+ in some extreme cases.

Overview

The total cost of a transaction (the "transaction fee") is the gas limit, multiplied by the gas price. Typically, if someone just says "Gas", they are talking about the "Gas Limit". You can think of the gas limit like the amount of liters/gallons/units of gas for a car. You can think of the gas price as the cost of that liter/gallon/unit of gas:

• With a car, it's $2.50 (price) per gallon (unit).
• With Ethereum, it's 20 Gwei (price) per gas (unit).

To fill up your "tank", it takes...

• 10 gallons at $2.50 = $25
• 21,000 units of gas at 20 Gwei = 0.00042 ETH.

Therefore, the total transaction fee will be 0.00042 Ether. Note that Gwei is just a unit of Ether, and is equal to 0.000000001 ETH. You can use the converter in this article to quickly convert from Gwei to Wei to Ether, which can be helpful when you want to know your transaction fee in ETH, rather than Gwei.

Gas Limit

The gas limit is called the limit, because it's the maximum amount of units of gas you are willing to spend on a transaction. This avoids situations where there is an error somewhere in a contract, and you spend way too much Ether. MyCrypto will automatically estimate how much gas your transaction will use.

However, the units of gas necessary for a transaction are already defined by how much code is executed on the blockchain. If you do not want to spend as much on gas, lowering the gas limit won't help. You must include enough gas to cover the computational resources you use, or your transaction will run out of gas. A standard transaction, from address A to address B with no contracts involved, will use a fixed amount of 21,000 gas.

All unused gas is refunded to you at the end of a transaction, so if you go to MyCrypto, send 1 ETH to our donation address, and use a gas limit of 400,000 you will receive 400,000 - 21,000 back. However, if you were sending 1 ETH to a contract, and your transaction to the contract fails, your transaction may use the entire 400,000, and you receive nothing back.

If your transaction runs out of gas, you can refer to our article on knowing which gas limit you should use.

Gas Price

If you want to spend less on a transaction, you can do so by lowering the amount you pay per unit of gas. The price you pay for each unit increases or decreases how quickly your transaction will be mined.

You can adjust the gas price with the slider on the transaction page. It will automatically determine the "best" gas price, by looking at current network activity.

If you want, you can also manually adjust the gas price, by clicking on "+ Advanced". For the current recommended gas prices, you can refer to ETH Gas Station.