How to calculate your average fuel consumption
The simple formula for average fuel consumption (l/100 km), a step-by-step example, what drives consumption up and how to bring it down.
The figure in the brochure is a lab number. The real consumption — the one that empties your wallet — you only learn by measuring it yourself. The good news: it is simple and takes a minute across two fill-ups.
The formula
Average consumption is expressed in litres per 100 km and is calculated like this:
How to measure it, step by step
- Fill the tank completely and note the odometer (or reset the trip counter).
- Drive normally for a few days, until the tank drops.
- Fill up completely again and note how many litres went in and how many km you drove since the last fill-up.
- Apply the formula: divide litres by km and multiply by 100.
Example: you put in 42 litres and drove 600 km. Consumption = (42 ÷ 600) × 100 = 7 l/100 km.
What pushes consumption up
- Aggressive driving — hard acceleration and braking
- Low tyre pressure
- High motorway speed (air resistance rises sharply)
- Air conditioning and extra weight in the boot
- Short trips with a cold engine
How to reduce consumption
- Drive smoothly, anticipate traffic, avoid needless acceleration
- Check tyre pressure monthly
- Remove useless weight and the roof rack when not in use
- At a steady cruising speed, use a higher gear
To see whether your changes actually help, you need a history. With Carvix you log your refuels and the app automatically computes your average consumption over time — you see in black and white whether it drops.
Track your real consumption, refuel by refuel. Free up to 3 cars.
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Why is my real consumption higher than the brochure figure?
Official figures are measured in ideal lab conditions. In real traffic — with stops, climbs, AC and your personal driving style — consumption is almost always higher.
Over what distance should I measure?
Ideally between two full fill-ups, then average over several refuels. The more km and the more readings, the more accurate the figure.
Does the dashboard reading show the correct consumption?
It is a good estimate for orientation, but it can differ from the real fill-up calculation. For the exact figure, use the litres-and-kilometres method.