Car & Vehicle

Fuel Consumption Calculator

Fuel consumption in litres per 100 km, measured from a tank - the unit most of the world quotes, where lower is better.

6 inputs Free, no sign-up

Your figures

What went in at the second fill-up. That is the amount the trip used, which is why the tank has to be filled to the same point both times.

The price you actually paid. Pump prices move daily and differ by several rupees between states, so the round number here is a placeholder, not a quote.

Try an example

Result

Your result

Enter your figures and the result appears here.

Estimates only. Rates, fees and specifications change. Confirm against the official source before you rely on a figure — see our disclaimer.

About this calculator

Litres per 100 kilometres runs the opposite way to kilometres per litre: here, lower is better. Europe, Australia and most manufacturers' technical documents use it, because fuel consumed over a fixed distance is the figure that adds up linearly when you plan a journey.

Measure it the same way as mileage — two fill-ups and a trip meter — and this page gives it in all four units so a figure quoted either way is usable.

How to use this calculator

  1. Fill the tank and reset the trip meter.
  2. Drive normally, then fill to the same point again.
  3. Enter the distance covered and the fuel it took.
  4. Read the consumption. A smaller number is a more economical vehicle.

The formula

Mileage (km/L) = Distance / Fuel used
L/100 km       = 100 / Mileage

That second line is a reciprocal, not a scale factor, and it is the single most common mistake in fuel-economy arithmetic. 20 km/L is 5 L/100 km. 10 km/L is 10 L/100 km. 5 km/L is 20. Halving the economy doubles the consumption — the two numbers cross at 10 and swap sides.

SymbolMeaningUnit
Distance Distance covered between fill-ups km or mi
Fuel used Fuel added to refill the tank L or gal

Worked example

420 km on 30 litres:

Mileage  = 420 / 30 = 14 km/L
L/100 km = 100 / 14 = 7.14

A vehicle at 5 L/100 km uses noticeably less than one at 7.14, and the difference over 15,000 km a year is more than 300 litres.

Notes and limits

  • Because consumption is linear in distance, differences at the thirsty end matter more than they look. Going from 15 to 14 L/100 km saves more fuel than going from 6 to 5, even though the second looks like a bigger improvement in percentage terms.
  • That is exactly the illusion km/L creates in reverse, which is why regulators in several countries moved to consumption units.
  • Manufacturers quote separate city, highway and combined figures. A single number without a cycle named beside it is not comparable with anything.
  • The mileage converter moves any figure between all four units without re-measuring.

What this calculation assumes

  • The tank was filled to the same level before and after.
  • The result is your measurement over one tank, not a rating.

Frequently asked questions

What is a good fuel consumption figure?

That depends entirely on the vehicle - a small hatchback and a seven-seat SUV are not comparable, and this page will not tell you what your car ought to achieve. What it will do is measure what yours actually does, which is the figure to track over time.

Is lower or higher better in L/100 km?

Lower. It counts fuel consumed over a fixed distance, so less is better - the opposite of km/L and mpg, where more distance per unit of fuel is better.

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

Divide 100 by the km/L figure. 20 km/L is 5 L/100 km. It is a reciprocal, not a multiplication, so there is no single factor that converts between them.

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