How Our Calculators Work
Every calculator on GasCalculator.org uses a published, checkable formula — the same formula is printed on the tool’s own page, and every worked example can be verified by hand:
- Fuel / trip cost: (Distance ÷ MPG) × Gas Price
- MPG: Distance ÷ Gallons used (or odometer difference ÷ gallons added)
- Cost per mile: Gas Price ÷ MPG
- EV cost per mile: Electricity price per kWh ÷ miles per kWh
- Unit conversions: 1 US gallon = 3.78541 litres; 1 mile = 1.60934 km; MPG ↔ L/100km via 235.215 ÷ MPG
Our Data Sources
- U.S. Energy Information Administration (EIA) — weekly retail gasoline and diesel prices, the reference source for US pump prices.
- Fueleconomy.gov / U.S. EPA — official city, highway and combined MPG ratings for vehicles sold in the US.
- IRS — the standard mileage rates referenced in our cost-per-mile guidance.
We never invent figures: where a page cites a price, rate or rating, it comes from one of the sources above or is clearly labelled as an illustrative example.
Review Process
Each calculator’s math is tested against hand-calculated cases before publication, and pages carry a “Reviewed” date. Content is re-checked when official rates change (for example, new IRS mileage rates each year). Errors reported by visitors are corrected as a priority.
Known Limitations
Our tools estimate fuel and energy costs from the inputs provided. They cannot account for your individual vehicle’s condition, real-time prices along a route, traffic, or driving style — which is why every result is an estimate, as our Disclaimer explains.
Last reviewed: October 23, 2026.