MPG & fuel economy calculator
Work out your car's MPG from miles driven and fuel used. See miles per litre, litres per 100km and fuel cost per mile if you add the amount spent.
Calculate your MPG
Enter the distance you drove and the fuel used. Use litres if you filled up at a UK pump, or UK gallons if you already have that figure.
What does MPG tell you?
MPG means miles per gallon. It shows how many miles your car travels for every UK gallon of fuel used. A higher MPG usually means better fuel economy and a lower fuel cost per mile.
The key UK detail is the gallon conversion. UK MPG is based on an imperial gallon, which is 4.54609 litres. That matters because petrol and diesel are sold in litres at UK forecourts.
For real-world results, measure from a full tank to the next full tank, note the miles driven, then use the litres added at the pump.
MPG formula
The calculator converts fuel into UK gallons, then divides your miles by those gallons.
If fuel is entered in litres:
UK gallons = litres ÷ 4.54609
MPG = miles driven ÷ UK gallons
Miles per litre = miles driven ÷ litres
Litres per 100km = (litres ÷ (miles × 1.60934)) × 100
Cost per mile = total fuel cost ÷ miles drivenIf you enter a total fuel spend, the calculator also works out pence per mile and the cost per 100 miles.
Worked MPG examples
Why your real MPG may be lower than advertised
Official MPG figures are measured in controlled test conditions. Your real result can be lower because of traffic, short journeys, cold starts, tyre pressure, roof boxes, heavy loads, aggressive acceleration and air conditioning use.
- Use a full-tank-to-full-tank method rather than guessing fuel used.
- Compare several tanks of fuel, not just one journey.
- Use the Fuel Cost Calculator to turn your MPG into a journey cost.
- Use the Commute Cost Calculator to estimate the annual cost of regular driving.
Want to see what that MPG means in real money?
MPG is useful, but cost per journey and cost per year are usually easier to act on. Use the fuel calculator next to estimate what your driving actually costs.
Calculatorz may earn a commission from selected partner links, but calculator results are free and independent.
MPG calculator FAQs
How do I calculate MPG from litres?
Divide litres by 4.54609 to convert to UK gallons. Then divide miles driven by the UK gallons used.
Does this use UK or US gallons?
This calculator uses UK imperial gallons. A UK gallon is larger than a US gallon, so UK MPG and US MPG are not directly interchangeable.
Can I use this for diesel?
Yes. Petrol and diesel cars both use MPG as a fuel-efficiency measure. Enter your miles driven and litres or UK gallons used.
What is a good MPG?
It depends on the vehicle. A small efficient car may return much higher MPG than a large SUV, van or performance car. Use your own real-world figures for a fair comparison.
Related glossary terms
These glossary pages explain the terms behind fuel efficiency and driving-cost calculations.