Recently, many friends have been confused about the concept of Gas on Ethereum, and this is actually a very good question. I was also overwhelmed by various explanations before, but I later realized that as long as you remember a simple formula, you can understand everything: Cost = Quantity × Price.

Actually, what is Gas? Simply put, it’s like gasoline needed for a car to run; all operations on the Ethereum network also require Gas to execute. You can think of Gas as the "fuel" for this blockchain network.

Let me explain in the most straightforward way. Suppose you want to drive from point A to point B, needing 10 liters of gasoline, and each liter costs 8 dollars. Then the cost is 10×8=80 dollars. Ethereum follows the same logic: sending a token might require 21,000 units of Gas, and if the price per Gas unit is 100 gwei, then the transaction fee is 21,000×100=2,100,000 gwei. Understand now?

The question of what Gas is actually combines three concepts: Gas Limit (the amount consumed), Gas Price (the unit price), and Gas Fee (the final cost). Gas Limit is the maximum amount of Gas you’re willing to pay; if the actual consumption is less than this limit, the excess is automatically refunded. But if the actual consumption exceeds the limit, the transaction will fail, and the Gas fee paid will not be refunded. So, don’t think about lowering Gas Limit to save money; that can backfire and cause more trouble.

Regarding Gas Price, it has become a bit more complicated after the upgrade. After the London upgrade in August 2021, Gas Price was divided into two parts: Base Fee and Max Priority Fee. The Base Fee fluctuates in real-time based on network congestion, while the Priority Fee can be adjusted by yourself to speed up the transaction. The final Max Fee is the sum of these two parts, similar to the Gas Price before the upgrade.

As for units, Gwei is the measurement unit for Ethereum, where 1 Gwei = 0.000000001 ETH. Why use Gwei to express Gas Price? Because saying “Gas Price is 10 Gwei” sounds much more natural than “Gas Price is 0.0000…1 ETH.”

Now, let’s look at actual calculations. Suppose you’re transferring via MetaMask, with a Gas Limit of 21,000 and a Max Fee of 63.97 Gwei. Then, Gas Fee = 21,000×63.97 = 1,343,454 Gwei, which equals 0.001343454 ETH. The estimated result provided by the system should be this amount.

Once you understand what Gas is, you’ll realize why sometimes Gas fees are so high. Ethereum’s block space is limited, and during high-demand periods like NFT auctions or popular projects, everyone is competing to get on the chain, causing Gas prices to skyrocket. In such cases, the smartest move is to wait and not rush into transactions.

Want to reduce Gas costs? First, check the current Gas prices in real-time. Second, if you’re not in a hurry, choose to operate during times when Gas prices are lower, usually in the afternoon to evening when it’s more stable. Third, consider using Layer 2 solutions or sidechains, such as Polygon, which offers much lower Gas fees, especially suitable for airdrops and interactive activities.

In summary, understanding what Gas is and how to calculate it is really important for safe and efficient transactions on Ethereum. Don’t get caught by high Gas fees—do more research and think carefully, and you can save a lot of money.