MPG Calculator

Q: How do I calculate MPG in the UK?

To calculate UK MPG: fill your tank, reset your trip meter, drive until you need to refuel, note the miles driven and litres used. MPG = Miles driven ÷ (Litres used ÷ 4.54609). For example: 300 miles driven, 40 litres used. 40 ÷ 4.54609 = 8.799 gallons. 300 ÷ 8.799 = 34.1 MPG.

Q: What is a good MPG for a UK car?

A good MPG depends on the car type. For a small hatchback (e.g. VW Polo), 45–55 MPG is typical. For a family saloon (e.g. Ford Mondeo), 35–50 MPG. For an SUV, 30–45 MPG. For a diesel car, 50–65 MPG is achievable. Sports cars may return 20–30 MPG. Hybrids typically achieve 55–80 MPG real-world, and pure EVs are rated in miles per kWh rather than MPG.

Q: How do I convert MPG to litres per 100km?

To convert UK MPG to l/100km: l/100km = 282.48 ÷ MPG. For example, 40 MPG = 282.48 ÷ 40 = 7.06 l/100km. To convert l/100km to UK MPG: MPG = 282.48 ÷ l/100km. This formula uses the UK gallon (4.54609 litres) — US MPG conversions use a different formula because the US gallon is only 3.785 litres.

Q: What is the difference between UK MPG and US MPG?

UK and US gallons are different sizes. 1 UK (Imperial) gallon = 4.54609 litres. 1 US gallon = 3.78541 litres. This means UK MPG figures are always higher than US MPG for the same vehicle. To convert US MPG to UK MPG: multiply by 1.20095. For example, 30 US MPG = 30 × 1.20095 = 36 UK MPG approximately.

Q: How do I calculate fuel cost for a journey?

Fuel cost for a journey = (Distance in miles ÷ MPG) × Litres per gallon × Fuel price per litre. Example: 100 miles, 40 MPG, fuel at 150p/litre. Gallons needed = 100 ÷ 40 = 2.5 gallons. Litres needed = 2.5 × 4.54609 = 11.37 litres. Cost = 11.37 × £1.50 = £17.05.

Q: Why is my real-world MPG lower than the official figure?

Official MPG figures are measured under controlled laboratory conditions using the WLTP (Worldwide Harmonised Light Vehicle Test Procedure) test cycle. Real-world driving typically achieves 10–30% less than WLTP figures because of higher speeds, aggressive acceleration, air conditioning use, cold engine operation, roof boxes, and heavier loads. The gap is typically larger for petrol cars than diesel.

Q: How can I improve my car's MPG?

To improve your fuel economy: maintain correct tyre pressure (under-inflation increases rolling resistance), drive smoothly and anticipate braking, keep to speed limits (every 10mph above 60mph significantly reduces MPG), remove unnecessary weight, use cruise control on motorways, avoid excessive idling, keep up with servicing (clean air filters, correct oil), and remove roof boxes/bike racks when not needed.

Last updated: February 2025 | Author: Mustafa Bilgic (MB)

Enter the distance you drove and the fuel used to calculate your MPG.

Distance Driven (miles) Fuel Quantity In Fuel Used

Enter your MPG and fuel price to find the cost of driving per mile or kilometre.

Your Car's MPG Fuel Price (pence per litre)

UK average petrol price approx. 143–150p/litre (Feb 2025). Diesel approx. 147–155p/litre.

Convert between UK MPG and litres per 100km (l/100km). Uses UK Imperial gallon (4.54609 litres).

Convert From UK MPG

Calculate the total fuel cost for a road trip or commute.

Journey Distance (miles) Your Car's MPG Fuel Price (pence per litre) Return Journey?

UK Average MPG by Car Type (2025)

Car Category	Typical Real-World MPG	l/100km	Example Models
Small City Car (Petrol)	45–55 MPG	5.1–6.3	VW Polo, Ford Fiesta, Vauxhall Corsa
Family Hatchback (Petrol)	38–50 MPG	5.7–7.4	VW Golf, Ford Focus, Toyota Auris
Family Saloon/Estate (Diesel)	45–60 MPG	4.7–6.3	BMW 3 Series, Ford Mondeo, Skoda Octavia
SUV (Petrol)	28–40 MPG	7.1–10.1	Nissan Qashqai, Kia Sportage, BMW X3
SUV (Diesel)	38–50 MPG	5.7–7.4	Land Rover Discovery Sport, Volvo XC60
Petrol-Electric Hybrid	50–70 MPG	4.0–5.7	Toyota Prius, Honda Jazz Hybrid, Yaris Hybrid
Plug-in Hybrid (PHEV)	100–300 MPG*	varies	Mitsubishi Outlander PHEV, BMW 530e
Sports Car (Petrol)	20–35 MPG	8.1–14.1	Porsche 911, Ford Mustang, BMW M3
Van (Diesel)	28–40 MPG	7.1–10.1	Ford Transit, VW Transporter, Mercedes Sprinter

*PHEV official MPG is unreliable as it depends heavily on how often the battery is charged. Real-world MPG with an uncharged battery is much lower.

What is MPG and How is it Measured?

Miles per gallon (MPG) is the primary measure of fuel efficiency used in the United Kingdom. Unlike most of Europe, which uses litres per 100 kilometres (l/100km), the UK has historically used the Imperial measurement system and continues to measure fuel economy in MPG. It represents how many miles a vehicle can travel on one UK (Imperial) gallon of fuel.

The UK gallon — also called the Imperial gallon — contains 4.54609 litres. This is different from the US gallon, which contains only 3.78541 litres, which is why UK and US MPG figures for the same car are different even when the underlying fuel consumption is identical.

Official UK MPG figures are now measured using the WLTP (Worldwide Harmonised Light Vehicle Test Procedure) test cycle, which replaced the older NEDC test in 2018. WLTP figures are generally more realistic than NEDC, but real-world fuel economy can still vary significantly from official figures depending on driving style, traffic conditions, road type and weather.

How to Calculate Your Real-World MPG

The most accurate way to measure your car's true fuel consumption is the brim-to-brim method:

Fill your tank completely to the brim
Reset your trip odometer to zero (or note the current odometer reading)
Drive normally until your fuel light comes on or until you want to refuel
Fill up again and note exactly how many litres you put in
Note the miles driven since you last filled up
Calculate: MPG = Miles driven ÷ (Litres added ÷ 4.54609)

Repeat this process over several fill-ups and calculate the average for a more accurate long-term figure, as a single tank can be skewed by whether you did mostly motorway or city driving.

MPG to l/100km Conversion Formula

The conversion formula between UK MPG and litres per 100km is based on the relationship between miles, kilometres, and the UK gallon:

1 mile = 1.60934 kilometres
1 UK gallon = 4.54609 litres
Therefore: l/100km = (4.54609 × 100) ÷ (1.60934 × MPG) = 282.48 ÷ MPG

For example: 40 MPG = 282.48 ÷ 40 = 7.06 l/100km. Conversely, 8 l/100km = 282.48 ÷ 8 = 35.3 MPG.

Frequently Asked Questions

How do I calculate MPG in the UK? +

Fill your tank, reset the trip meter, drive until you refuel, then note miles driven and litres used. MPG = Miles driven ÷ (Litres used ÷ 4.54609). Example: 300 miles, 40 litres used. 40 ÷ 4.54609 = 8.799 gallons. 300 ÷ 8.799 = 34.1 MPG.

What is a good MPG for a UK car? +

Small hatchback: 45–55 MPG is good. Family saloon: 35–50 MPG. SUV petrol: 28–40 MPG. Diesel estate: 45–60 MPG. Hybrid: 55–70 MPG. Above 50 MPG for a petrol car is generally considered excellent. Below 30 MPG for a non-sports car is considered poor.

How do I convert MPG to litres per 100km? +

l/100km = 282.48 ÷ MPG. Example: 40 MPG = 282.48 ÷ 40 = 7.06 l/100km. To reverse: MPG = 282.48 ÷ l/100km. This formula is specific to the UK Imperial gallon. US MPG uses a different conversion because the US gallon is smaller.

What is the difference between UK MPG and US MPG? +

UK Imperial gallon = 4.54609 litres. US gallon = 3.78541 litres. UK MPG is always about 20% higher for the same car. To convert US MPG to UK MPG: multiply by 1.20095. Example: 30 US MPG = approx. 36 UK MPG.

How do I calculate fuel cost for a journey? +

Formula: Cost = (Miles ÷ MPG) × 4.54609 × (price in pence ÷ 100). Example: 100 miles, 40 MPG, 148p/litre. Gallons needed = 100 ÷ 40 = 2.5. Litres = 2.5 × 4.54609 = 11.37. Cost = 11.37 × £1.48 = £16.82.

Why is my real-world MPG lower than the official figure? +

Official WLTP figures are measured in controlled lab conditions. Real-world driving is affected by higher motorway speeds, urban stop-start, air conditioning, cold weather, roof boxes, extra passengers, and driving style. Expect 10–30% less than the official figure in typical UK conditions.

How can I improve my car's MPG? +

Maintain correct tyre pressure, drive smoothly and anticipate braking, avoid speeds above 60mph on motorways (each 10mph over 60 adds significant fuel consumption), remove unnecessary weight, use air conditioning sparingly, keep up with servicing, and remove roof boxes when not needed.

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Mustafa Bilgic (MB)

Financial content writer and calculator specialist at UK Calculator. All tools use official HMRC and government data. Learn more about our team.

MPG Calculator — Miles Per Gallon UK