Fuel economy calculator
Turn a trip into litres per 100 km, miles per gallon, and a fuel cost.
Result
Fuel economy calculator
- Units
- Metric (km and litres)
- What you know
- Fuel used
Trip cost
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Enter the trip and a fuel price, or try the example.
Ballpark estimate, check before you buy or quote.
Unit conversions use the international mile (1.609344 km) and the US gallon (3.785411784 L), from NIST Special Publication 811. As of 2026-10-02.
Estimate for planning only. This is not tax, legal, accounting or financial advice. Results depend on the figures you enter. Check all numbers, rates and rules with the official source or a qualified professional before relying on them.
How this works and common questions
About this tool
Enter a distance and either the fuel you used or a consumption rate, plus the price you pay. The result is the fuel cost for that trip, with litres per 100 km and miles per US gallon beside it.
How it works
If you know the fuel used, the cost is that amount times your price. If you know a rate, the tool first works out the fuel from the distance. Litres per 100 km and miles per gallon use the international mile and the US gallon.
Rules
Litres per 100 km and miles per gallon round to 1 decimal, half up. Money rounds to the cent, half up. A half cent rounds away from zero. You type the price. This is not a tax or a mileage allowance. Conversions follow NIST Special Publication 811: 1 mile = 1.609344 km and 1 US gallon = 3.785411784 L. As of 2026-10-02. https://www.nist.gov/pml/special-publication-811
Questions
Which gallon does this use?
The US liquid gallon, 3.785411784 litres, as defined by NIST. The page shows that figure and the date.
How is the trip cost worked out?
Fuel used times the price you type. If you enter a rate, the tool works out the fuel from the distance first.
Does this use a government fuel price?
No. You type the price. Nothing here is a tax or a mileage allowance.
Do I need an account?
No. The tools work without one. You only need to sign in to save your work.
Is what I type saved?
No. Nothing is saved unless you sign in and choose Save. Otherwise it stays on the page.
Do you show ads or sell my information?
No. We show no ads and we do not sell your information.
Is this tax or legal advice?
No. Results are estimates for planning. Check rates and rules with the official source or a qualified professional.
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Estimate for planning only. This is not tax, legal, accounting or financial advice. Results depend on the figures you enter. Check all numbers, rates and rules with the official source or a qualified professional before relying on them.