Gas Efficiency Calculator
Gas efficiency calculator works out Converted economy and Converted unit from Distance travelled, Fuel used and Fuel price. The default figures on this page give converted economy of 28.0000; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
5 steps
- Distance 350 mi = 563.2704 km; fuel 12.5 gal-us = 47.3176 L.
- Economy = 563.2704 km / 47.3176 L = 11.90402 km/L.
- 11.904024 km/L = 28 mpg-us.
- Fuel for 350 mi = 563.2704 km / 11.904024 km/L = 47.3176 L = 12.5 gal-us.
- Cost = 12.5 gal-us x 3.6 = 45, i.e. 0.1286 per mi.
Its 7 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
4 sources
What the gas efficiency calculator calculates
Converts between miles per gallon (US and imperial), kilometres per litre and litres per 100 km, and works out trip fuel use, fuel cost and measured economy from distance and fuel volume.
How to use this gas efficiency calculator
Enter Distance travelled, Fuel used and Fuel price. Converted economy updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Converted economy, Converted unit and Miles per US gallon.
The method follows NIST Handbook 44, Appendix C - General Tables of Units of Measurement, NIST Special Publication 811, Guide for the Use of the International System of Units (SI), Weights and Measures ACT 1985 (UK), Schedule 1 and US EPA, Fuel Economy Guide - Fuel Economy and Annual Fuel Cost calculations.
What you can compare
Change one input at a time to see how it affects Converted economy, Converted unit and Miles per US gallon. The inputs you can vary are Distance travelled, Fuel used and Fuel price.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How to calculate fuel efficiency in miles per gallon?
Converts between miles per gallon (US and imperial), kilometres per litre and litres per 100 km, and works out trip fuel use, fuel cost and measured economy from distance and fuel volume. Open “How this is worked out” beside the result to see each step for your own figures.
How many miles is $30 of gas?
On the figures this page opens with — distance travelled 350, fuel used 12.5 and fuel price 3.6 — the converted economy is 28. No single number fits everyone: change any figure above and the answer updates as you type, with each step of the arithmetic beside it.
What information do I need for the gas efficiency calculator?
You need Distance travelled, Fuel used and Fuel price. The page opens with default figures that give converted economy of 28.0000, so you can see the scale before entering your own.
What does this gas efficiency calculator show?
It shows Converted economy, Converted unit, Miles per US gallon, Miles per imperial gallon, Kilometres per litre, Litres per 100 km, Miles per litre and Kilometres per US gallon, with the working and any warnings for your entries.
Can I check how the gas efficiency calculator result was calculated?
Yes. The “How this is worked out” section shows the calculation steps, and the sources section identifies the references used for the method.