Today, most cars are issued with a nifty little piece of equipment called a trip computer. Most modern **trip computers** will record, calculate, and display the distance travelled, the average speed, average fuel consumption, and instant fuel consumption. In most cases, it will tell you your range, ie. how many more kilometres you can travel before you need to fill up. However, if your car is slightly older and without a trip computer, you will have to rely on simple mathematics to get a more realistic idea.

Also, if you go according to the manufacturer’s consumption figures, remember that they are (mostly) a little optimistic. When they tell you it’s 5.0 litres per 100 km, you can almost add 2 litres to that figure for a more realistic idea of fuel economy. In some cases it’s not a huge difference, so don’t use this as a rule of thumb. For the purposes of this article, I will be using the Suzuki Baleno as a practical example to assist in my explanation.

I work with litres per 100 km, but many people understand the km-per-litre system better. In the US and UK, it’s miles per gallon or MPG – yet the two countries have different gallon sizes!

If litres per 100 km figures don’t make sense to you, you can use an online converter to find out how many kilometres you’ll get on one litre of petrol, and vice versa. Or, you can just do a simple calculation as per the table below.

**To convert ** ** Formula to use**

km per litre to litres per 100 km | divide 100 by km per litre |

litres per 100km to km per litre | divide 100 by litres per 100 km |

Let’s say, for example, that your trip computer (or the manufacturer’s website) says your specific car uses 8.0 litres of fuel per 100km. The actual formula to get km per litre is 100 divided by 8 = 12.5, meaning that your car will give you 12.5 km on one litre.