How to use the Gas Mileage Calculator
The gas mileage calculator finds fuel economy from miles driven and fuel used.
Open the Gas Mileage Calculator →
What you need to enter
- Distance (miles)
- Fuel used (gallons)
The formula
mpg = miles ÷ gallons. L/100 km = 235.215 ÷ mpg.
Worked example
Using the default values in the calculator:
- Distance (miles): 350
- Fuel used (gallons): 12.5
| Miles per gallon (US) | 28 |
| Litres per 100 km | 8.4 |
| Km per litre | 11.9 |
Tips for better results
- Fill up at the same pump each time.
- Track over several tanks.
Common mistakes to avoid
- Estimating from one short trip.
- Mixing US and UK gallons.
Please note: Results are estimates for general use. For safety-critical work such as electrical or building projects, check with a qualified professional and local codes. See our Disclaimer.