GWEI

GWEI is a term for a very small unit of ethereum cryptocurrency (ETH), and is commonly used to determine the transaction fee (gas fee) on the Ethereum blockchain. One GWEI equals to 0.000000001 ETH.

GWEI is commonly used in relation to the chain fees charged to conduct a transaction. These fees are calculated in GWEI based on the transaction type and chain load at a given time. Since these fees are usually a small ETH fraction, it is much easier to use GWEI to determine one’s gas fee.

The Ethereum blockchain team decided to use the name Wei for the smallest ETH unit as a tribute to Wei Dai, a computer scientist who made significant contributions to the cryptography and cryptocurrencies development. Variations on the name "Wei" then introduced other ethereum units, including GWEI.
GWEI means Gigawei, which is a combination of the words "giga" and "Wei". There is 1 billion Wei in one GWEI.

Wei and its distribution:

Depending on the type of transaction, you may be able to influence its speed by adjusting the amount of GWEI paid.

Wei and its distribution:

UNITS Wei value
Wei 1 Wei
Kwei 1 000 Wei
Mwei 1 000 000 Wei
GWEI 1 000 000 000 Wei
Twei 1 000 000 000 000 Wei
Pwei 1 000 000 000 000 000 Wei
ETH 1 000 000 000 000 000 000 Wei

Depending on the type of transaction, you may be able to influence its speed by adjusting the amount of GWEI paid.

You can see in the picture that if you want a faster transaction, you will pay 27 GWEI. If you're not in a hurry, just pay 24 GWEI. You can find this quick overview at Coingecko or for more details see Ethgasstation.

Important to know

Since one GWEI is 0.000000001 ETH, the value of one GWEI in USD varies according to the ETH token price.

For example, the dollar value of 50 GWEI today may not be the same as 50 GWEI tomorrow. You can calculate the GWEI value at any time based on the current ethereum price.

Ethereum blockchain gas fees also vary. When the blockchain is overloaded, gas fees rise. When there is less load, gas fees are lower. If you need to have a transaction confirmed quickly, it is better to pay extra GWEI for the faster transaction. This ensures that  your transaction will be processed faster. But if you're not in a hurry and you don't mind a 10-minute delay (or longer, depending on network conditions), then you'll do fine to pay the minimum GWEI fee.

PROs

• Ease of use: the gas fee is built into the chain, so you don't have to do any calculations or pre-planning unless you want to work on reducing transaction fees
• No pre-purchase required: the ETH amount is automatically deducted from your crypto wallet after the transaction

CONs

• It can be expensive: if you want a fast transaction or if you want to send a transaction during a heavy chain load, the cost can be very high

Calculating the gas fee in GWEI (how much ETH you will need to pay for the transaction) is very simple:
Maximum gas limit x how much GWEI is needed to pay = number of GWEI you will convert to ETH.
Example:
gas limit x fee in GWEI that you want to pay = the result
21 000 x 150 = 3 150 000 GWEI
Divide the resulting number by 1 billion (because 1 GWEI is one billionth of ETH).
3 150 000 / 1 000 000 000 = 0.00315 ETH (chain gas fee)
If you want to send 1 ETH and the chain's gas fee is GWEI 150, 1.00315 ETH will leave your crypto wallet.

Conclusion

GWEI is a good unified system to determine the gas fee per transaction. We don't have to recalculate decimal numbers and we can find out the price in ETH with a simple calculation.