Calculate real-world UK miles per imperial gallon from the distance driven and litres of fuel used.
Real-world MPG changes with traffic, speed, weather, tyre pressure, vehicle load and driving style. Use several fill-ups for a more representative average.
How to use the MPG Calculator UK
Enter the miles driven and the litres of fuel used over the same period. For the most reliable fill-to-fill result, fill the tank, reset the trip counter, drive normally, refill to a similar level and enter the trip mileage and litres shown on the pump.
UK MPG formula
| Result | Calculation |
|---|---|
| Imperial gallons used | Litres used ÷ 4.54609 |
| UK MPG | Miles driven ÷ imperial gallons used |
| Litres per 100 km | Litres used ÷ kilometres driven × 100 |
| Kilometres per litre | Kilometres driven ÷ litres used |
UK MPG versus US MPG
This calculator uses the UK imperial gallon, which contains about 4.54609 litres. The US gallon is smaller, so UK MPG and US MPG are not interchangeable. A vehicle will show a higher numerical MPG figure when measured with imperial gallons.
Understanding the result
A higher MPG means the vehicle travels farther on one imperial gallon. A lower litres-per-100-kilometres result also indicates better fuel economy. These two measures move in opposite directions, even though both describe the same consumption.
Official figures and real-world MPG
The Vehicle Certification Agency explains that official fuel-consumption results are shown in both MPG and litres per 100 kilometres, and that laboratory figures provide a consistent basis for comparison. Check the VCA fuel-consumption guide when comparing published vehicle data. Your measured result may differ because normal roads and driving conditions vary.
How to get a more accurate MPG reading
Measure across several journeys rather than one short trip. Refill at the same pump position where practical, avoid rounding the litres, and use the trip counter rather than estimating the distance. Tracking several full tanks reduces the effect of small filling differences.
Related calculators
Turn your MPG result into an estimated journey bill with the Fuel Cost Calculator UK. For a broader view of ownership expenses, use the Car Running Cost Calculator UK. Browse all tools on the United Kingdom Calculator homepage.
Frequently asked questions
Does this calculator use imperial gallons?
Yes. UK MPG is calculated with the imperial gallon, equal to approximately 4.54609 litres.
Can I use one short journey?
You can, but a longer measurement across a full tank usually gives a more stable real-world result.
Why is my MPG lower than the official figure?
Traffic, cold starts, short journeys, speed, hills, weather, vehicle load and tyre pressure can all reduce real-world MPG.
Is higher MPG better?
Yes. A higher MPG means the vehicle covers more miles for each imperial gallon used.
How often should I calculate MPG?
Checking each fill-up and comparing a rolling average can show longer-term changes more clearly than one isolated result.