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Fuel Consumption Calculator

Work out your car's real fuel consumption from the distance you drove and the fuel you used, in L/100 km, km/L and US MPG.

kilometres

Kilometres driven since you last filled the tank.

litres

Litres it took to fill the tank back up.

Results

Fuel consumption

6.5 L/100 km

Litres used to drive 100 km. Lower is better.

Distance per litre
15.38 km/L
Fuel economy (US MPG)
36.19 MPG (US)

Fuel consumption 6.5 litres per 100 kilometres. 15.38 kilometres per litre. 36.19 miles per US gallon.

Formula

Fuel consumption (L/100 km)
= fuel used (L) ÷ distance (km) × 100
Distance per litre (km/L)
= distance (km) ÷ fuel used (L)
Fuel economy (US MPG)
= 235.214583 ÷ fuel consumption (L/100 km)

L/100 km and km/L describe the same thing in opposite directions: fuel per distance and distance per fuel. 235.214583 converts L/100 km to miles per US gallon (100 × 3.785411784 litres per US gallon ÷ 1.609344 km per mile).

Worked example

You filled the tank, drove 500 km, and it took 32.5 litres to fill it up again.

  1. Step 1: Fuel consumption

    32.5 ÷ 500 × 100 = 6.5 L/100 km

  2. Step 2: Distance per litre

    500 ÷ 32.5 = 15.38 km/L

  3. Step 3: US MPG

    235.214583 ÷ 6.5 = 36.19 MPG

The car used 6.5 litres per 100 km, which is 15.38 km per litre or 36.19 miles per US gallon.

How to measure your fuel consumption

The fill-up (or tank-to-tank) method measures the fuel your car actually used, so it reflects your own driving rather than an official test:

  • Fill the tank until the pump clicks off, then reset the trip meter.
  • Drive as you normally would. A longer distance gives a more reliable figure.
  • Fill the tank again until the pump clicks off. The litres you add are the fuel you used.
  • Enter the trip distance and those litres into the calculator.

Getting a more accurate figure

Pumps do not click off at exactly the same level every time, so a single short measurement can be a little off. Adding up the distance and fuel over several fill-ups and entering the totals evens this out.

If you drive a mix of town and motorway, measure over a period that includes both, or measure each separately to see how much they differ.

L/100 km, km/L and MPG

L/100 km is the litres used to drive 100 km, so lower is better. km/L and MPG are the distance you can drive on a fixed amount of fuel, so higher is better. Different countries quote different units, so the calculator shows all three.

MPG here is US MPG, based on the US gallon of 3.785411784 litres. UK MPG uses the larger imperial gallon of 4.54609 litres, so a UK MPG figure for the same car is about 20% higher.

Why your figure may differ from the official one

Official figures come from standard laboratory test cycles so that cars can be compared fairly. Real-world consumption depends on speed, traffic, load, weather, tyre pressures and driving style, and is often higher than the official figure.

Frequently asked questions

How do I calculate fuel consumption?

Divide the litres of fuel used by the kilometres driven and multiply by 100 to get L/100 km. For example, 32.5 litres over 500 km is 32.5 ÷ 500 × 100 = 6.5 L/100 km.

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

Divide 100 by the L/100 km figure. For example, 6.5 L/100 km is 100 ÷ 6.5, or about 15.38 km per litre.

Is a lower L/100 km better?

Yes. L/100 km is how much fuel the car needs to cover 100 km, so a lower number means the car uses less fuel. For km/L and MPG it is the other way round: higher is better.

Why is my result different from my car's trip computer?

Trip computers estimate fuel use from engine data, while the fill-up method measures the fuel you actually put in. The two can differ slightly, and the trip computer may cover a different period from the one you measured.

Can I enter miles and gallons instead?

This calculator uses kilometres and litres. If you measured in miles and US gallons, use the MPG calculator, which also shows the L/100 km equivalent.

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