Gwei

Gwei is a tiny unit of ether, Ethereum’s native currency. One gwei is one-billionth of an ether, and it is the unit gas fees are usually quoted in.

How it works

Because a full ether is a large amount relative to the cost of a single transaction, fees are expressed in gwei to keep the numbers readable. When you send an Ethereum transaction, you pay a gas price measured in gwei per unit of gas; the total fee is that price multiplied by the gas the transaction consumes.

Why it matters

Gwei is the practical unit users watch to judge how expensive the network is at any moment. When the network is busy, gas prices in gwei rise as users compete to have their transactions included sooner.

Example

A wallet might estimate a transaction’s gas price at 20 gwei when the network is quiet and far higher when it is congested.