I just realized that many newcomers to crypto still don't fully understand what gas fees are, so I want to share a bit of experience.

In short, gas fees are the amount of money you pay to miners to confirm your transaction on the blockchain. Every action on the chain — whether sending tokens, executing smart contracts, or launching applications — consumes the network's computational resources. Miners have to bear this cost, so they need to be compensated. That’s the purpose of gas fees.

The interesting thing is that gas fees are not always the same. They vary depending on the blockchain you use. On Ethereum, you pay with ETH. On BSC, you pay with BNB. Each network has its own token for this purpose.

One thing to note is that you must pay the gas fee whether your transaction succeeds or fails. Why? Because even if the transaction fails, miners still need to verify and process it, which requires computational resources. So, the computational cost must be paid by someone.

Gas fees play an important role in maintaining the network’s operation. They incentivize miners to actively confirm transactions and also help block malicious transactions. However, when the network is congested, gas fees can spike, making it difficult for users.

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 action 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 fees to earn more profit. That’s why gas fees increase.

Want to know how much the gas fee is? It’s very simple. When you send a transaction on MetaMask, for example, you’ll see an estimated processing fee on the confirmation screen. You can choose to speed it up by paying a higher fee or keep it as is. After sending, you can check the final gas fee using Etherscan by entering the transaction hash into the search bar.

The calculation of transaction fee is quite straightforward: Tx Fee = Gas Limit multiplied by Gas Price.

Gas price is the amount of tokens you’re willing to pay per unit of gas. On Ethereum, Gwei is commonly used as the unit (1 Gwei = 0.000000001 ETH). If you set the gas price to 20 Gwei, that means you pay 0.00000002 ETH per gas unit. Want your transaction confirmed quickly? Increase the gas price. Want to save? Lower it. The higher the gas price, the more priority your transaction gets.

Gas limit is the maximum number of gas units you’re willing to spend on a transaction. It’s like a buffer to protect you from contract errors. However, lowering the gas limit doesn’t save you much. You need to provide enough gas to cover the computational resources used; otherwise, the transaction will fail with an Out of Gas error. The spent fee will be deducted. If the transaction completes and the actual gas used is less than the gas limit, you only pay for the gas actually consumed. For standard transactions, the gas limit is usually 21,000.

Let’s use a simple example: Suppose you drive from Hanoi to Ho Chi Minh City, needing 21,000 liters of gasoline, with the price at 20,000 VND/liter. The total cost is 21,000 liters × 20,000 VND = 420 million VND. Similarly, the ETH transaction fee is 21,000 (gas limit) multiplied by 20 Gwei (gas price) = 420,000 Gwei, which equals 0.00042 ETH.

In summary, gas fees are essentially the necessary costs to keep the blockchain network running. If your transaction is urgent, set a higher gas price to prioritize it. If not, just set a reasonable gas price. Understanding how gas fees are calculated will help you manage your transaction costs more effectively on the blockchain.