I just received a question from a newcomer to crypto: what is gas fee and why does it change frequently? Today I will explain it in detail for you.

First of all, what is a gas fee? Simply put, it is the fee you pay for miners to verify and process your transaction on the blockchain. Every action on the blockchain, whether transferring tokens, executing smart contracts, or launching DApps, consumes computational resources. Miners have to bear this cost, so they need to be compensated. That’s why gas fees exist.

The interesting part is that these gas fees vary depending on the blockchain you use. On Ethereum, you pay with ETH. On BNB Chain, you pay with BNB. Each network has its own token for this purpose.

An important point: gas fees are charged even if the transaction fails. Why? Because miners still need to verify and attempt to execute the transaction, whether it has errors or not. The computational work must be done, so the cost still accrues.

The role of gas fees is not only to compensate miners. It also helps keep the network stable and prevents malicious transactions. However, when the network is congested, gas fees spike, making it difficult for users. That’s the downside of the system.

Now, why do gas fees fluctuate? There are two main factors. First is the complexity of the transaction or contract. If you perform a complex contract with many steps, the gas fee will be higher. Second is network congestion. When there are too many pending transactions, miners prioritize those paying higher gas fees to earn more money.

In terms of calculation, the transaction fee is computed as: Transaction Fee = Gas Limit × Gas Price. I will explain each part.

Gas Limit is the maximum amount of gas units you are willing to spend on a transaction. It’s like telling the miner: I allow you to use up to this much gas for this transaction. This prevents errors in the contract. For standard transactions, Gas Limit is usually 21,000 units. If the transaction completes and consumes less gas than the Gas Limit, you only pay for the actual gas used. But if the gas runs out, the transaction fails with an Out of Gas error, and the gas already used is deducted.

Gas Price is the amount of tokens you are willing to pay per unit of gas. On Ethereum, the common unit is Gwei, where 1 Gwei = 0.000000001 ETH. If you set the gas price at 20 Gwei, it means you pay 0.00000002 ETH per gas unit. Want your transaction to confirm faster? Increase the gas price. Want to save costs? Lower the gas price. The gas price determines how quickly your transaction gets verified.

Let me give a concrete example for clarity. Suppose you want to send ETH via MetaMask. You’ll see an estimated processing fee on the confirmation screen. You can choose to speed up by paying a higher gas fee or opt for a cheaper option. After sending, you can check the final gas fee on Etherscan by entering the transaction hash in the search bar.

I’ll use a simple analogy: Gas Limit is like the liters of fuel needed for a car to travel from Hanoi to Ho Chi Minh City, say 21,000 liters. Gas Price is like the price per liter of fuel, say 20 dong. So, the fuel cost is 21,000 × 20 = 420,000 dong. Similarly, ETH transaction fee = 21,000 (Gas Limit) × 20 Gwei (Gas Price) = 420,000 Gwei. Converting to ETH: 420,000 × 0.000000001 = 0.00042 ETH.

In summary, what is a gas fee? It’s the fee you pay for the blockchain to verify your transaction. The calculation depends on Gas Limit and Gas Price. If your transaction is urgent, increase the gas price. If not in a rush, set a reasonable gas price. Understanding this mechanism will help you manage your transaction costs more effectively in the crypto world.