Gwei
Definition
The smallest commonly used denomination of Ether (ETH), equal to 0.000000001 ETH. Used to express gas prices on Ethereum — the cost of executing transactions and smart contracts.
Gwei is to Ether what cents are to dollars, but much smaller. One ETH equals one billion gwei (1,000,000,000 gwei). The name comes from "giga-wei," where wei is the smallest possible unit of ETH (1 ETH = 10^18 wei). Gwei is the standard unit for expressing Ethereum gas prices.
Gas prices fluctuate based on network demand. During quiet periods, gas might cost 5-15 gwei. During high demand (popular NFT mints, market volatility), gas can spike to 100-500+ gwei. A simple ETH transfer uses about 21,000 gas, so at 20 gwei, the fee is 21,000 x 20 gwei = 420,000 gwei = 0.00042 ETH.
Smart contract interactions cost more gas than simple transfers. A token swap on Uniswap might use 150,000-300,000 gas. An NFT mint might use 100,000-200,000 gas. Complex DeFi operations can use millions of gas. At high gwei prices, these transactions can cost $50-$500+.
EIP-1559 (London Upgrade, August 2021) changed Ethereum's fee mechanism. Gas fees now have a base fee (set by the network, burned) and a priority tip (paid to validators). The base fee adjusts up or down based on whether blocks are more or less than 50% full, making fees more predictable.
Understanding gwei is essential for managing Ethereum costs. Using the network during off-peak hours (typically early morning US time, weekends), setting reasonable gas limits, and using Layer 2 networks for smaller transactions can dramatically reduce the fees you pay.
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Related Terms
Frequently Asked Questions
How do I find the current gwei price?
Gas trackers like Etherscan's gas tracker or GasNow show real-time gwei prices. Most wallets (MetaMask, Rabby) display current gas estimates before you confirm a transaction. Lower gwei means cheaper transactions, so timing transactions during low-activity periods saves money.
What's a reasonable gwei price to pay?
For non-urgent transactions, 10-25 gwei is typical during calm periods. Above 50 gwei, consider waiting unless the transaction is time-sensitive. For urgent transactions during high demand, you may need to pay 100+ gwei. Layer 2 networks offer transactions for fractions of a gwei equivalent.