Fuel Economy Converter

1. Enter the value you want to convert.
2. Choose the from unit.
3. Choose the to unit.
4. Read the result, plus km per litre and L/100km.

Here is what each result means:

Fuel economy describes how far a vehicle travels for a given amount of fuel, or how much fuel it uses over a distance. It is measured in different units around the world, which makes comparing cars across countries confusing. The United States uses miles per gallon, the United Kingdom uses a larger imperial gallon, and much of the rest of the world uses litres per 100 kilometres.

There is an important twist: some units measure distance per fuel and others measure fuel per distance, and these are inverses of each other. Miles per gallon and kilometres per litre go up as a car gets more efficient, while litres per 100 kilometres goes down. That is why you cannot simply multiply by a fixed factor to move between all of them.

This converter handles the inverse relationship automatically. It first works out the economy in kilometres per litre, then converts to whichever unit you choose, so a value in miles per gallon and one in litres per 100 kilometres line up correctly for the same car.

It bridges every unit through kilometres per litre.

1. Your value is converted to kilometres per litre, a common base.
2. For litres per 100 km, the converter takes 100 divided by that figure.
3. For the other units, it multiplies or divides by the fixed gallon-and-mile factors.

For running costs, see the fuel cost calculator, or convert distances with the length converter.

Convert 30 US mpg to litres per 100 km.

Result: 30 US mpg is about 12.75 kilometres per litre, which is roughly 7.84 litres per 100 km. The same car is about 36 UK mpg, because the imperial gallon is larger.

Two measure distance per fuel, two the other way round.

For miles per gallon and kilometres per litre, a bigger number means a more efficient car. For litres per 100 kilometres it is the opposite: a smaller number is better, because the car uses less fuel to cover the distance.

The two gallons are not the same size, which changes the mpg figure.

Because the imperial gallon is about 20 percent larger, the same car shows a higher figure in UK mpg than in US mpg. This is a common source of confusion when comparing cars advertised in different countries, and it is why the two mpg units are kept separate.

The Direction of the Units

Converting between distance-per-fuel and fuel-per-distance units means taking a reciprocal, not just scaling.

Which Gallon

US and imperial gallons differ in size, so US mpg and UK mpg are not the same.

The Value Itself

Very low economy gives a very high litres-per-100 km figure, and the reverse.

Comparing Cars

Put a US mpg figure and a European litres-per-100 km figure on the same basis.

Travel and Imports

Read a car's economy in the unit you are used to.

Budgeting

Work out economy before estimating fuel costs for a trip.

1. Treating L/100km Like Mpg

They move in opposite directions. A higher mpg is a lower litres per 100 km.

2. Mixing US and UK Mpg

The imperial gallon is larger, so UK mpg is higher than US mpg for the same car.

3. Multiplying by a Single Factor

You cannot convert between all units with one factor because of the inverse relationship.

4. Forgetting Which Is Better

For litres per 100 km, lower is better; for the mpg and km/L units, higher is better.

5. Entering Zero or a Negative

Economy must be greater than zero to convert.

Conversions use the standard gallon, mile and litre definitions, handling the inverse units correctly.

Convert mpg to kilometres per litre, then take 100 divided by that figure. 30 US mpg is about 12.75 km/L, which is roughly 7.84 litres per 100 km.

Miles per gallon measures distance per unit of fuel, while litres per 100 km measures fuel per unit of distance. As one rises the other falls, so they are reciprocals.

The imperial (UK) gallon is about 20 percent larger than the US gallon, so the same car shows a higher figure in UK mpg than in US mpg.

Lower is better. A smaller litres-per-100 km figure means the car uses less fuel to travel the distance, so it is more economical.

A US gallon is about 3.785 litres and an imperial (UK) gallon is about 4.546 litres. That difference is why the two mpg figures differ.

It depends on the vehicle, but many efficient cars manage under 6 litres per 100 km, which is roughly 40 US mpg or 47 UK mpg.

Divide km per litre by the factor for the mpg unit: about 0.425 for US mpg or 0.354 for UK mpg. This converter does it for you.

No. Electric vehicle efficiency is usually measured in energy per distance, such as kWh per 100 km, which is a different kind of unit.

No. The calculation runs in your browser and nothing you enter is stored or sent anywhere, unless you choose Save, which keeps the result only on this device.

• Fuel economy in automobiles (Wikipedia).
• Gallon (Wikipedia).
• Fuel efficiency (Wikipedia).