How to Calculate Ethereum Gas Fees
On Ethereum, you pay for **computation and storage** in **gas**, priced in **Gwei** per gas unit. Simple transfers use ~21,000 gas; DeFi interactions use far more. **L2s** batch transactions—fees are often lower but include bridge costs.
Core formula
Fee = gas used × gas price · Gwei = 10⁻⁹ ETHStep by step
1. Estimate gas units
Wallets estimate gas limit—ETH transfer ~21k; swaps often 150k–250k+ depending on route.
2. Set gas price (Gwei)
Base fee + priority tip. Higher Gwei = faster inclusion in congested blocks.
3. Convert to ETH/USD
Fee ETH = gas × Gwei × 10⁻⁹. Multiply by ETH/USD for dollar cost.
Mainnet vs L2 vs other chains
Compare total cost including bridges and failed-tx gas.
- Ethereum L1: Highest security/cost; fee spikes at congestion.
- Rollups (L2): Lower per-tx fee; add bridge time/cost.
- Failed transactions: You can still pay gas for reverts on L1.
- NFT/mint spikes: Gas wars during drops—model worst-case Gwei.
Use our calculators
Common mistakes
- Using transfer gas for swap estimates
- Ignoring L1 bridge fees
- Setting max fee too low and stalling
FAQ
What is Gwei?
10⁻⁹ ETH; gas prices are quoted in Gwei per gas unit.
Why did fee differ from estimate?
Actual gas used can be below limit; price can move before confirmation.