Gas units and gas price
Two numbers determine what you pay. Gas units measure how much computation your transaction needs — a simple transfer is cheap, a complex DeFi interaction is not. Gas price is what you bid per unit, and it floats with demand. Total cost is units multiplied by price.
A simple ETH transfer uses 21,000 gas units. At a gas price of 20 gwei, that is 0.00042 ETH. The same transaction at 200 gwei during heavy congestion costs ten times more — for identical work.
Why fees spike
- A popular NFT mint or token launch flooding the network at once.
- Sharp market moves driving liquidations and arbitrage.
- Peak activity hours overlapping across major regions.
- MEV bots bidding aggressively for transaction ordering.
How to pay less
Timing helps: weekend and off-peak hours are consistently cheaper. Layer 2 networks such as Arbitrage-style rollups settle to the main chain while charging a fraction of the fee, and for many use cases they are the correct default rather than an optimisation.
Batching several actions into one transaction and setting a maximum fee you are willing to pay both avoid the worst outcomes during congestion.
Fees are not the same everywhere
Different chains price block space very differently. Comparing a fee in isolation is meaningless without also comparing settlement guarantees, liquidity and how much of your activity actually needs the most secure chain.