How the fuel consumption calculator works
Last updated 10 November 2026
Your own consumption is the figure to use in every running cost calculation. It takes two numbers to find: the distance you drove and the fuel you put in.
How it works
- Litres per 100 km = litres ÷ distance × 100.
- Kilometres per litre = distance ÷ litres.
Worked example
With the starting figures:
- The starting figures give 8.0 litres per 100 km.
- That is 12.5 kilometres per litre.
Your own number beats the brochure
Every running-cost sum starts with how much fuel your car uses. Brochure figures come from test conditions, and real driving is rarely the same. It takes two numbers to find your own: the distance you drove and the fuel you put in. This calculator turns them into litres per hundred kilometres and kilometres per litre.
How to measure it
- Fill the tank to the first click and note the odometer, or reset the trip meter.
- Drive as you normally do until the tank is low.
- Fill up again at the same pump, to the first click, and note the litres.
- Enter the distance and the litres.
Reading the result
Litres per hundred kilometres is the number most people use in South Africa, and a lower number means a more economical car. Kilometres per litre is the same thing the other way round, and a higher number is better. The tool shows both so you can compare with figures from any source.
Why the number varies
- City driving, short trips and traffic use more fuel than steady highway driving.
- A loaded car, a roof rack and an open window raise consumption.
- Low tyre pressure and a poorly tuned engine raise it too.
- Altitude, heat and air conditioning also change the figure.
- One tank gives a rough number. Averaging several tanks is more accurate.
Use it in other calculators
Once you have your number, use it in the fuel cost calculator and the road trip cost calculator. The figures you type stay in your browser.
A worked idea
Say you drove a distance of a few hundred kilometres and put in a number of litres at the next fill-up. Divide the litres by the distance and multiply by a hundred to get litres per hundred kilometres. Do this on several tanks and take the average, because one tank is affected by how you drove that week.
Things to watch
- Fill up at the same pump and stop at the first click for repeatable results.
- A lower number means a more economical car.
Use the result in the fuel cost calculator. Read the full disclaimer.