MPG Calculator
Work out your vehicle's real-world fuel efficiency from your latest fill-up. Enter the miles you've driven and the litres it took to refill, and see your actual MPG instantly.
Use your trip meter or note the odometer before and after.
Check your fuel receipt for the exact amount.
Add the price to see your cost per mile. Check current prices
How It Works
Fill your tank to the top, reset your trip meter (or note the odometer reading), then drive normally until your next fill-up. When you refuel, fill to the top again and note how many litres went in. Enter both numbers above and the calculator converts them to miles per imperial gallon — the standard UK measure of fuel efficiency.
The formula is straightforward: divide the miles driven by the number of imperial gallons used (litres ÷ 4.546). The result is your real-world MPG, which may differ from the manufacturer's quoted figure due to driving style, traffic, weather, and tyre condition.
Why Manufacturer MPG Figures Differ
Official MPG figures are measured under standardised lab conditions (WLTP). Real-world driving typically returns 10–20% lower efficiency because of factors like cold starts, short journeys, air conditioning, roof loads, and stop-start traffic. Tracking your actual MPG over several fill-ups gives a much more accurate picture of your running costs.
Tips to Improve Your MPG
- Keep tyres properly inflated — under-inflated tyres increase rolling resistance, reducing efficiency by up to 3%.
- Accelerate gently — shift up early and avoid harsh throttle inputs. Staying in the highest comfortable gear saves fuel.
- Anticipate traffic — lift off the throttle early rather than braking late. Coasting in gear uses zero fuel on most modern cars.
- Reduce drag — remove roof bars and boxes when not in use. At motorway speeds, aerodynamic drag is the biggest fuel cost.
- Avoid short cold trips — engines are least efficient in the first few miles. Combine errands into one trip where possible.
- Service your car regularly — a clean air filter, fresh oil, and properly gapped spark plugs all contribute to better efficiency.
- Fill up at the cheapest forecourt — use our comparison tool to find the best prices near you.