Fuel Economy Converter
Convert between Miles per gallon (US), Miles per gallon (UK), Kilometer per liter and more — step-by-step working shown.
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Common conversions from Miles per gallon (US)
Showing common units only. See all 7 units on unitconvert.to →
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What is Fuel Economy?
Fuel economy measures how efficiently a vehicle uses fuel. It tells you how far you can travel on a certain amount of fuel, or how much fuel you need to travel a certain distance. Understanding your vehicle's fuel economy helps you manage running costs, compare different models, and consider your environmental impact.
The main challenge with fuel economy is the variety of units used worldwide. You might see Miles Per Gallon (MPG), Litres per 100 kilometres (L/100km), or Kilometres per Litre (km/L). Crucially, the 'gallon' in UK MPG is different from the 'gallon' in US MPG, which can lead to confusion if not converted correctly.
How to Convert MPG (UK) to L/100km Manually
Convert Miles to Kilometres
Start with your MPG (UK) value. This means 'miles per UK gallon'. First, convert the miles to kilometres. Since 1 mile = 1.60934 kilometres, multiply your MPG (UK) by 1.60934. Example: If your car gets 40 MPG (UK), then 40 miles * 1.60934 km/mile = 64.3736 km. So, your car travels 64.3736 km per UK gallon.
Convert UK Gallons to Litres
Next, convert the UK gallon into litres. One UK gallon is equal to 4.54609 litres. Continuing the example: Your car travels 64.3736 km per 4.54609 litres.
Calculate Litres per 100 Kilometres
Now you have kilometres per litre. To get litres per 100km, first find litres per km by dividing the litres by the kilometres (from Step 2). Then, multiply that result by 100. Example: 4.54609 litres / 64.3736 km = 0.07062 litres/km. Then, 0.07062 litres/km * 100 = 7.06 L/100km. So, 40 MPG (UK) is approximately 7.06 L/100km. Formula: L/100km = (100 * 4.54609) / (MPG_UK * 1.60934)
Conversions in context
Family Car (UK)
45 MPG UK → 6.28 L/100km
Road Trip (US)
30 MPG US → 24.98 MPG UK
Delivery Van (Europe)
8.5 L/100km → 33.24 MPG UK
Motorbike (Asia)
35 km/litre → 2.86 L/100km
Older Car (UK)
28 MPG UK → 9.91 km/litre
Hybrid Car (US)
55 MPG US → 4.28 L/100km
Common mistakes to avoid
- My car gets 50 MPG, which is great! My friend's car gets 40 MPG, so mine is much better:This statement assumes both cars are using the same 'MPG' standard. If your car is rated in US MPG and your friend's in UK MPG, the comparison is inaccurate. 50 US MPG is actually less efficient than 50 UK MPG. To compare accurately, convert both figures to the same standard, for example, both to UK MPG or both to L/100km. 50 US MPG is about 41.6 UK MPG, so your friend's 40 UK MPG car is actually slightly less efficient than your 50 US MPG car.
- I want a car with a high L/100km rating because that means it's more efficient:L/100km (Litres per 100 kilometres) measures how much fuel you use over a set distance. A higher number means you are using more fuel, indicating lower efficiency. For L/100km, a lower number is better, as it means the car consumes less fuel to travel 100 kilometres. For example, 5 L/100km is more efficient than 10 L/100km.
- My car does 15 km/litre, so it's more efficient than a car that does 30 MPG:You cannot directly compare km/litre with MPG without converting them to a common unit. 'MPG' could be UK or US, and the units themselves are different (distance per volume vs. distance per volume, but with different base units). Convert both figures to a single unit, such as L/100km or MPG (UK). For example, 15 km/litre is about 6.67 L/100km. If '30 MPG' refers to 30 UK MPG, that's about 9.42 L/100km. In this case, 15 km/litre (6.67 L/100km) is more efficient than 30 UK MPG (9.42 L/100km).
Questions people ask
What is the difference between UK MPG and US MPG?
The difference lies in the size of the gallon. A UK (Imperial) gallon is 4.546 litres, while a US gallon is 3.785 litres. This means a car rated at 30 UK MPG is more fuel-efficient than a car rated at 30 US MPG, as it travels the same distance on a larger volume of fuel.
What is a good MPG for a UK car?
A 'good' MPG depends on the car type and age. For a modern petrol family car in the UK, anything above 45-50 MPG (UK) is generally considered good. Smaller city cars or hybrids can achieve 60-70+ MPG (UK), while larger SUVs or performance cars might be in the 20-35 MPG (UK) range.
How do I calculate my fuel economy from a fill-up?
To calculate your fuel economy, note your mileage (odometer reading) when you fill up your tank. Drive until your next fill-up, then note the new mileage and the amount of fuel you put in. Subtract the old mileage from the new mileage to get the distance travelled. Divide the distance travelled by the amount of fuel used to get your fuel economy (e.g., miles per litre or km per litre).
Is a lower or higher L per 100km better?
A lower L per 100km (Litres per 100 kilometres) is better. This unit indicates the amount of fuel consumed to travel a specific distance. Therefore, a smaller number means the vehicle uses less fuel and is more efficient.
How do I compare electric car efficiency to petrol MPG?
Electric car efficiency is typically measured in kWh per 100km or miles per kWh. To compare with petrol MPG, you can convert both to a common unit like 'cost per mile' or 'CO2 emissions per mile'. Alternatively, you can use an 'eMPG' (equivalent MPG) figure, which estimates how many miles an electric car could travel on the energy equivalent of one gallon of petrol.