Fuel consumption calculator
Real-world consumption in litres per 100 km from a full tank fill.
Calculator inputs
Results
Enter your values and press “Calculate” to see the result.
In short
- What it calculates
- Real-world consumption in litres per 100 km from a full tank fill.
- Formula used
L/100 km = litres ÷ km × 100- Example
- 520 km on 34 litres:
Fuel consumption calculator
Official consumption figures rarely match reality. The reliable way to measure is to fill the tank, zero the trip meter and fill up again at the next stop.
Those two numbers give you the true consumption of your own driving.
How it works
Fuel used is divided by the distance covered and multiplied by a hundred. Miles per gallon are also shown, handy for comparing with US and UK specifications.
Formula
L/100 km = litres ÷ km × 100
km/L = km ÷ litres
mpg (US) = 235.215 ÷ (L/100 km)
mpg (UK) = 282.481 ÷ (L/100 km)
Worked example
520 km on 34 litres:
Consumption: 34 ÷ 520 × 100 = 6.54 L/100 km
km/L: 15.29
US mpg: 35.97
Explanation
Why real consumption never matches the brochure
Official figures come from a laboratory cycle at controlled temperature, with no wind, no hills, no air conditioning and no luggage. The WLTP cycle, used in Europe since 2018, is closer to reality than the old NEDC, but still sits below what the trip computer shows in normal use.
What drives consumption up most
Speed, above everything: air resistance grows with the square of speed, so going from 100 to 130 km/h can raise consumption by thirty per cent. Then come short journeys from cold, where the engine burns far more until it reaches temperature, and underinflated tyres.
How to measure properly
Fill the tank until the pump clicks off, zero the trip meter, drive normally for several hundred kilometres and refill at the same pump to the same cut-off. Litres refuelled divided by kilometres gives real consumption. The trip computer tends to flatter the figure.
Litres per hundred and miles per gallon
They are inverse measures: one measures consumption and the other efficiency. A car improving from 8 to 6 litres per hundred saves far more than one going from 5 to 4, even though the gap looks the same.
Frequently asked questions
Why is my real consumption higher than the official figure?
Because homologation cycles run in controlled conditions. Traffic, air conditioning, load and driving style raise consumption by 10% to 30%.
How do I measure consumption properly?
Fill to the pump’s first click, note the odometer, and repeat exactly the same procedure at the next fill-up.
How much does driving faster raise consumption?
Aerodynamic drag grows with the square of speed. Going from 100 to 130 km/h can increase consumption by around thirty per cent.
Can I trust the trip computer?
As a reference yes, but it usually shows slightly optimistic figures. Measuring with two full tanks at the same pump is more reliable.
Need to calculate something else?
These tools are often used alongside this calculator.
Trip cost
Fuel, tolls and the split between everyone in the car.
Average speed
The average speed of a journey in km/h, m/s and miles per hour.
Litres to gallons
Turn volumes from litres into US gallons.
Km to miles
Turn any distance from kilometres into statute miles using the official factor.