Recently, a friend asked me what gas is, and I realized that many beginners are really confused about this concept. I used to be the same way—there are all kinds of explanations online, some say it’s a quantity, some say it’s a fee, which makes people even more confused. Actually, just remember a simple formula: Fee = Quantity × Price. Everything makes sense.

Let me give you the easiest analogy to understand. If you drive from point A to point B and need 10 liters of gasoline, with each liter costing 8 dollars, then the total cost is 80 dollars. The same logic applies to executing operations on Ethereum: sending tokens requires consuming 21,000 units of Gas, and if the Gas price is 100 gwei, then the fee is 21,000 × 100 = 2,100,000 gwei.

So, what is gas? Simply put, gas is the “fuel” for executing various operations on Ethereum. If you want to transfer tokens, interact with smart contracts, or store data, you need to pay for gas. Just like a car can’t run without gasoline, Ethereum can’t do anything without gas.

I often hear people say, “Gas is now $5” or “Gas has skyrocketed to 200,” but what they’re really referring to is the Gas price (unit price), not the quantity of gas or the final fee you pay. This detail is very important—many people lose out because they confuse these concepts.

What about Gas Limit? It’s simply the maximum amount of gas you’re willing to spend on a transaction. For example, a transfer actually only needs 21,000 gas, but if you set the Gas Limit to 50,000, the remaining 29,000 will be refunded to you. Conversely, if the actual required gas is 51,000 but you only set 50,000, the transaction will fail, and you won’t get back the 50,000 you paid. So don’t think about lowering the Gas Limit to save money; that can actually cause losses.

Regarding the unit of Gas price, it’s more convenient to use Gwei. 1 Gwei = 0.000000001 ETH. If you use ETH directly, the zeros can be confusing. After the London upgrade, Gas price consists of a base fee plus a Max priority fee (tip). The base fee fluctuates in real-time based on network congestion, and you can adjust the tip yourself. The more tip you give, the higher the priority of your transaction, and the easier it is to get included in a block. It’s like tipping a driver on Didi during peak hours to get a faster ride.

Finally, let’s calculate the Gas fee. Suppose I transfer with MetaMask, with a Gas Limit of 21,000 and a Gas price of 63.97 gwei. The Gas fee is 21,000 × 63.97 = 1,343,454 gwei, which is 0.0013434 ETH. This number doesn’t seem large, but if Ethereum is congested and the Gas price spikes to hundreds of gwei, the fee can be shocking.

Why are Gas prices sometimes so high? Mainly because Ethereum’s block space is limited. During high-demand periods—like virtual land rushes or a popular project airdrop—everyone is trying to get on-chain, and Gas prices surge. The best strategy then is to wait. If it’s not urgent, choose a cheaper time to transact. Usually, late afternoon to evening is more stable, and from 7 PM to the next morning, prices tend to rise.

There are a few ways to reduce Gas fee expenses. First, check the current Gas price before operating—don’t act blindly. Second, if it’s not urgent, wait for a cheaper time. Lastly, consider using Layer 2 or sidechains like Polygon, which have extremely low Gas fees—especially suitable for airdrops and interactions. Some even jokingly call it the “beggar chain,” because its costs are much cheaper than Ethereum.

In summary, not understanding what Gas is or how Gas prices fluctuate can cause you to lose money when operating on Ethereum. Always carefully check your Gas settings before any transaction—this can really save you a lot.