Miles Per Gallon (MPG) Calculator
Calculate your car's real-world fuel efficiency from a tank fill-up. Compare against manufacturer claims and typical values for petrol, diesel, and hybrid vehicles.
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MPG and Fuel Efficiency Guide
What's the difference between Real-World and Official MPG?
Official MPG figures from WLTP (Worldwide Harmonised Light Vehicle Test Procedure) testing are closer to real-world figures than the old NEDC test they replaced, but still typically 10–20% higher than real-world driving. Factors that reduce MPG below the official figure: cold engine starts (the first few miles of each journey are significantly less efficient), motorway speeds above 70mph, short urban trips, air conditioning, roof boxes, tyre under-inflation, and carrying heavy loads. Urban driving with frequent stop-start traffic is typically where the gap between official and real-world MPG figures is widest, since official tests don't fully replicate genuine city conditions.
What do I need to know about Typical MPG Ranges?
Small petrol (1.0–1.2L): 45–60 mpg real-world. Medium petrol (1.5–2.0L): 35–50 mpg. Diesel: typically 10–15% better than equivalent petrol — medium diesel 45–60 mpg. Hybrid (e.g. Toyota Prius, Yaris): 55–70 mpg in mixed driving. Plug-in hybrid: 100–250+ mpg on official figures (misleading — depends heavily on charging frequency). Large SUV petrol: 25–35 mpg. Large diesel SUV: 35–50 mpg. Sports car: 20–35 mpg. These are indicative — real figures depend on driving style and conditions more than any single published number can capture.
What do I need to know about Improving Your MPG?
The single biggest factor in fuel economy is driving style — smooth acceleration and anticipating stops can improve efficiency by 15–25%. Specific techniques: maintain a buffer behind traffic to coast rather than brake; use cruise control on motorways (reduces throttle hunting); shift up early in manual cars (most efficient at 1,500–2,000 RPM for most engines); avoid excessive idling (turn engine off if stopped for over 30 seconds); maintain correct tyre pressures, since 10% under-inflation adds roughly 2% to fuel consumption — a small but consistent drag that adds up over regular driving.
What do I need to know about Comparing Fuel Types?
At current UK prices, comparing cost per mile: petrol at 45 mpg and 150p/litre: 18.6p/mile. Diesel at 55 mpg and 155p/litre: 15.8p/mile. Electric (3.5 miles/kWh) at 7p/kWh (off-peak): 2.0p/mile. Electric at 25p/kWh (home day rate): 7.1p/mile. The cost advantage of electric vehicles is dramatically affected by whether you can charge off-peak at home. Public rapid charging at 70p/kWh: 20p/mile — more expensive than petrol or diesel for most cars.