What Are Ethereum Gas Fees? (And How to Pay Less)
6 min read · Updated July 22, 2026
Every action on Ethereum — sending ETH, swapping tokens, minting an NFT — costs a fee called 'gas'. If you've ever wondered why a simple transfer sometimes costs a few cents and other times tens of dollars, this guide explains exactly how gas works and how to keep your costs down.
What is gas on Ethereum?
Gas is the unit that measures how much computational work a transaction requires. Ethereum's network is a shared computer, and gas is how it meters usage so that no single person can hog its resources for free.
Every operation has a fixed gas cost. A basic ETH transfer always uses 21,000 gas. A token swap on a DEX might use 150,000 gas because it touches more smart-contract code. You pay for the amount of gas your transaction uses, multiplied by the current price of gas.
What is gwei?
Gas prices are quoted in 'gwei', a tiny denomination of ETH. One gwei is 0.000000001 ETH (one-billionth). Quoting fees in gwei keeps the numbers readable — saying '20 gwei' is far easier than writing out the fraction of an ETH.
Your total fee is roughly: gas used × gas price (in gwei). For example, a 21,000-gas transfer at 20 gwei costs 420,000 gwei, which is 0.00042 ETH. Multiply by the ETH price to get the dollar cost.
Why do gas fees change so much?
Gas prices are set by supply and demand for block space. When lots of people transact at once — a popular NFT mint, a market crash, a token launch — demand spikes and fees rise. When the network is quiet, fees fall.
Since the EIP-1559 upgrade, each block has a 'base fee' that automatically adjusts up or down based on how full recent blocks were. You can add a 'priority fee' (a tip) on top to get included faster.
How to pay lower gas fees
Time your transactions. Gas is usually cheapest on weekends and during off-peak hours (late night US time). A live gas tracker shows you when prices dip.
Use Layer-2 networks. Rollups like Arbitrum, Optimism and Base process transactions off the main chain and settle in batches, cutting fees by 90% or more for the same actions.
Set a lower priority fee for non-urgent transactions. If you don't need instant confirmation, the 'low' tier will still confirm — just more slowly.
Batch your actions where possible, and avoid transacting during known high-demand events like major mints.