MPG Calculator
Work out your car's real miles per gallon from the fuel you have actually used. Enter the distance covered and the fuel added to see how your economy compares with the official figure.
What The MPG Calculator Tells You
- Your real MPG based on the fuel you have actually used
- An L/100km figure the metric equivalent, handy for comparisons
- An economy rating a quick sense of how your figure stacks up
- A baseline to track so you can spot a sudden drop over time
How MPG Is Calculated
Miles per gallon tells you how far your car travels on one gallon of fuel. In the UK we buy fuel in litres but still measure economy in imperial gallons, so the calculator does the conversion for you.
It takes the miles driven, divides by the litres used, then multiplies by 4.546, the number of litres in an imperial gallon. So 280 miles on 40 litres works out at roughly 31.8 MPG.
Your real figure will almost always be lower than the official MPG quoted when the car was new, because everyday driving involves traffic, hills, cold starts and the weight you carry. A gap of 10 to 20 percent is normal.
What Can Change Your MPG?
Fuel economy moves around in normal use. The best comparison is usually your own car against its previous results.
| MPG factor | How it can affect economy |
|---|---|
| Driving style | Hard acceleration, late braking and high speeds usually reduce MPG. |
| Journey type | Short trips, cold starts and stop-start traffic use more fuel. |
| Vehicle condition | Tyre pressure, servicing, wheel alignment and extra weight can all affect economy. |
How To Work Out Your MPG
Fill up, drive, then enter two numbers.
Fill Up And Reset The Trip
Brim the tank and set your trip meter to zero.
Drive As Normal
Carry on until you next need fuel.
Enter Miles And Litres
Use the trip reading and the pump receipt, and the calculator does the rest.
What Our Expert Says
Free tools like these put official DVLA and DVSA data straight into drivers' hands. Used alongside a quick insurance comparison, they help you make a more informed decision about a vehicle before you commit, whether you are buying, selling or simply keeping your own car on the road.Co-Founder, Clean Green Cars
MPG Calculator FAQs
Why Is My MPG Lower Than The Official Figure?
Official figures come from lab tests, so almost every car returns less in real driving. Short trips, cold weather, traffic and a heavy right foot all reduce economy. A gap of 10 to 20 percent is typical.
How Can I Improve My Fuel Economy?
Smoother acceleration, correct tyre pressures, removing unnecessary weight and keeping up with servicing can all help. A sudden fall in MPG can point to under-inflated tyres or a car due a service.
Should I Brim The Tank Each Time?
For the most accurate reading, fill to the same point every time, ideally until the pump first clicks off.
Does MPG Affect My Insurance?
MPG itself does not, but your annual mileage can. Giving an accurate mileage when you compare quotes helps make sure you are quoted fairly.
Useful Resources
- GOV.UK - Get Vehicle Information From DVLA - Check what vehicle details DVLA holds, including tax, MOT, fuel type and emissions data.
- GOV.UK - Check Vehicle Tax - Check whether a vehicle is taxed, when tax is due and whether it has been registered as off the road.
- GOV.UK - Check MOT Status - Check whether a vehicle has a valid MOT certificate and when the current MOT runs out.
- GOV.UK - Check MOT History - View past MOT results, recorded mileage, failures, advisories and certificate downloads.
- TfL - Check Your Vehicle - Check London ULEZ, LEZ and other charging rules for a vehicle.
