I just saw someone ask what Ethereum's gas is, and I found that the explanations online vary widely—some say it's consumption quantity, others say it's the cost of consumption. Beginners can indeed get confused easily. Actually, just remember a simple formula: Cost = Quantity × Price, and everything else becomes easy to understand.

Let me give you an example first. Just like a car needs gasoline to run, various operations on the Ethereum network also require paying gas to execute. Suppose you drive from point A to point B and need 10 liters of gasoline, costing 8 dollars per liter—that's a fuel cost of 10×8=80 dollars. Similarly, sending tokens on Ethereum consumes 21,000 units of gas. If the gas price is 100 gwei per unit, then the transaction fee is 21,000×100=2,100,000 gwei. This is the logic behind calculating gas fees.

So when you hear someone say "gas is now 5" or "gas has skyrocketed to 200," they are actually talking about the gas price, not the quantity or the fee. Gas itself is a technical term representing the fuel needed to perform an operation.

Then, how can you know how much gas a transaction will cost? This involves two concepts: Gas Limit and Gas Price. Gas Limit is the maximum amount of gas you're willing to pay for. Different operations consume different amounts of gas; more complex actions require more gas. Wallet software like MetaMask will automatically provide an estimated value. If the actual consumption is less than this limit, the excess will be refunded. But if the actual consumption exceeds your set limit, the transaction will fail, and the gas fee already paid will not be refunded. So never try to lower the Gas Limit to save money, as that often backfires.

As for Gas Price, this is the unit price of gas. Ethereum uses Gwei as the denomination—1 Gwei equals 0.00000001 ETH. Why use Gwei instead of ETH? Because saying "gas price is 10 Gwei" sounds much more natural than "gas price is 0.00000001 ETH."

After the London upgrade, calculating gas fees became a bit more complex. Now, Gas Price includes two parts: Base Fee and Tip. The Base Fee fluctuates in real-time based on network congestion, while the Tip is adjustable by you. Adding a tip can prioritize your transaction to be included faster, similar to tipping a driver for quicker service. The sum of these two parts is your final gas price.

In actual calculation, it's quite simple: Gas Fee = Gas Limit × Gas Price. For example, if Gas Limit is 21,000 and Gas Price is 63.97 gwei, then the fee is 21,000×63.97=1,343,454 gwei, which equals about 0.001343 ETH.

Why are gas fees sometimes so high? Mainly because Ethereum's block space is limited. When everyone is competing to get on-chain—for example, for NFTs or virtual real estate—competition drives up the gas price. The best way to deal with this is to wait it out. If you're not in a rush, try to operate during times when gas prices are lower. Usually, the afternoon to evening has more stable gas, and after 7 PM, it might rise again.

To reduce gas costs, besides timing your transactions well, you can also consider using other Layer 2 networks or sidechains. Almost all Ethereum applications can now be deployed on networks like Polygon or Arbitrum, where gas fees are much lower. Polygon is sometimes jokingly called the "beggar chain" because of its extremely cheap fees, making it especially suitable for airdrops and interactions, in stark contrast to the high gas on the Ethereum mainnet.

In summary, once you understand what gas is, how to calculate it, and when it's cheap, you'll be able to operate more smartly on Ethereum and save a lot of money. If you have time, you can check real-time gas prices across different chains on Gate to stay informed before making a move.