How L/100 km is calculated

Litres per 100 kilometres (L/100 km) answers a simple question: for every 100 kilometres you drive, how many litres of fuel does your vehicle use? The formula is: litres used ÷ kilometres driven × 100.

Worked example

If you use 42 litres over 560 kilometres, the calculation is 42 ÷ 560 × 100 = 7.5 L/100 km. That is the same figure used in this site's main example: 350 km at 7.5 L/100 km needs 26.25 litres.

How to measure your own figure

Fill the tank completely and reset the trip meter (or note the odometer). Drive normally until you fill up again, and record both the litres added and the kilometres covered since the last full tank. Divide litres by kilometres and multiply by 100. One tank gives a rough figure; averaging over three or four tanks gives a much more reliable one, because a single fill can vary with pump cut-off and driving mix.

What about km per litre?

Kilometres per litre is the same information flipped around: kilometres driven ÷ litres used. A vehicle at 7.5 L/100 km travels about 13.3 km per litre (100 ÷ 7.5). Neither figure is better in itself — Australia generally uses L/100 km, so this site uses that as its main input, and you can convert if your handbook uses the other form.

Why your figure changes

Your L/100 km is not a fixed property of the car. City traffic, cold starts, air conditioning, load, roof racks, hills, and speed all move it. That is why a single measured figure from one kind of driving should not be used for a very different trip — use the multi-leg calculator with a different consumption for each leg, and keep a fuel log to learn your own averages over time.