How do I convert km/L to L/100 km?

Divide 100 by the km/L figure. A car that does 20 km/L uses 100 ÷ 20 = 5 litres per 100 km.

How do I convert km/L to mpg?

Multiply by about 2.352 for US mpg or about 2.825 for UK (imperial) mpg. So 15 km/L is about 35.28 US mpg or 42.37 UK mpg.

Why are US and UK mpg different?

They use different gallons. A US gallon is about 3.785 litres and a UK gallon about 4.546 litres, so the same car shows a higher mpg figure in UK gallons.

Is a higher L/100 km figure better?

No. L/100 km measures fuel used, so lower is better. km/L and mpg measure distance per fuel, so higher is better.

How do I measure my car's real mileage?

Fill the tank fully, reset the trip meter, drive normally, then fill up again. Divide the kilometres driven by the litres needed to refill.

km/L to L/100 km and mpg: How to Convert Fuel Efficiency

The short answer

To convert km/L to L/100 km, divide 100 by the km/L figure: 20 km/L is 100 ÷ 20 = 5 L/100 km. The same formula works backwards: 8 L/100 km is 100 ÷ 8 = 12.5 km/L. To get US mpg, multiply km/L by about 2.352; for UK mpg, multiply by about 2.825. The free Fuel Efficiency Converter converts between all of these in one step.

Three ways to describe the same car

Different countries quote fuel efficiency differently:

Unit	Meaning	Better is	Common in
km/L	Kilometres driven on one litre	Higher	India and several other countries
L/100 km	Litres used to drive 100 km	Lower	Europe, Australia, Canada
mpg (US)	Miles per US gallon	Higher	United States
mpg (UK)	Miles per imperial gallon	Higher	United Kingdom

The key difference: km/L and mpg are distance per fuel, while L/100 km is fuel per distance. That is why the conversion between them is a division (an inverse), not a simple multiplication.

Conversion table

These figures come from the Fuel Efficiency Converter.

km/L	L/100 km	US mpg	UK mpg
10	10	23.52	28.25
12	8.33	28.23	33.90
15	6.67	35.28	42.37
18	5.56	42.34	50.85
20	5	47.04	56.50
25	4	58.80	70.62

Worked examples

Example 1: A hatchback is rated at 18 km/L. What is that in L/100 km?

100 ÷ 18 = 5.56 L/100 km.

Example 2: A review says a car uses 6 L/100 km. What is that in km/L?

100 ÷ 6 = 16.67 km/L. In US mpg, the converter gives 39.2.

Example 3: A US car is rated 30 mpg. What is that in Indian terms?

30 × 0.425144 = 12.75 km/L (the converter shows 12.7543), or 7.84 L/100 km.

Example 4: A UK review quotes 40 mpg. Is that the same as 40 US mpg?

No. 40 UK mpg is 14.16 km/L, while 40 US mpg is about 17.01 km/L. Always check which gallon a figure uses.

How to use the converter

Enter your figure in Value to convert.

Pick its unit in From: Kilometers/liter, Liters/100km, Miles/gallon (US), Miles/gallon (UK) or Kilometers/US gallon.

Pick the unit you want. The result appears in the green box.

The All Fuel Efficiency conversions table below shows the figure in every unit; click a row to copy it.

Results are rounded to four decimal places. The converter treats 1 US mpg as 0.425144 km/L and 1 UK mpg as 0.354006 km/L.

Why L/100 km is better for comparing cars

Because km/L is an inverse measure, equal-looking improvements save very different amounts of fuel:

Going from 10 to 12 km/L saves 10 − 8.33 = 1.67 litres every 100 km.
Going from 20 to 22 km/L saves 5 − 4.55 = 0.45 litres every 100 km.

Both are "+2 km/L", but the first saves almost four times as much fuel. When you are comparing running costs, convert both cars to L/100 km and compare litres.

Working out fuel cost per kilometre

Once you know km/L, cost per km is simple:

Cost per km = fuel price per litre ÷ km/L

For example, if fuel cost ₹100 a litre (an example figure; check your local price), a car doing 15 km/L costs 100 ÷ 15 = ₹6.67 per km. A 300 km trip would use 300 ÷ 15 = 20 litres, or ₹2,000 of fuel.

How to measure your real mileage

Official figures come from standardised lab tests, and real driving often differs. The tank-to-tank method gives you your own number:

Fill the tank until the pump clicks off. Don't top up beyond the click.

Reset the trip meter to zero.

Drive normally until you need fuel, ideally for a few hundred kilometres.

Fill up again at the same pump if possible, stopping at the first click, and note the litres.

km/L = kilometres on the trip meter ÷ litres added.

Repeat it over two or three fills and average the results, because one tank can be skewed by a long highway run or heavy traffic.

Why your mileage differs from the rated figure

If your tank-to-tank result is lower than the brochure figure, these are the usual reasons:

City traffic. Frequent stopping and idling uses fuel without covering distance.
Air conditioning. Running the AC adds load to the engine, especially in slow traffic.
Speed. Air resistance rises sharply with speed, so steady, moderate highway speeds are usually more efficient than fast driving.
Tyre pressure. Under-inflated tyres increase rolling resistance. Check pressure when the tyres are cold.
Load and roof racks. Extra weight and anything that disturbs airflow both cost fuel.
Short trips. A cold engine runs less efficiently until it warms up.

Use the same method each time you measure, so you are comparing like with like.

Common mistakes

Multiplying instead of dividing for L/100 km. It is 100 ÷ km/L, not 100 × km/L.
Mixing US and UK mpg. UK figures look about 20% higher for the same car.
Comparing km/L gains directly. Convert to L/100 km to see real fuel saved.
Treating "Kilometers/US gallon" as km/L. It is per gallon, about 3.785 times larger than km/L.
Typing 0. The converter only makes sense with a positive number.

Related tools

For speeds rather than fuel use, read how to convert km/h to m/s or open the Speed Converter. The Volume Converter converts litres and gallons directly, and the Percentage Calculator helps you work out how much more efficient one car is than another.