Calculating Fuel Consumption: Litres per 100 km and Costs
Measure real consumption with the full-tank method, work out fuel costs for a trip, read manufacturer figures correctly and convert consumption values.
Car & Mobility5 linked calculatorsReading time: 6 min.
The trip computer estimates, the fuel receipt knows. Fill up twice, note the kilometres and you know your car's real consumption – and can work out the cost of any trip from it.
Key takeaways
- Consumption in l/100 km = litres filled ÷ kilometres driven × 100.
- The full-tank method over several fill-ups is the most accurate.
- Fuel costs = kilometres ÷ 100 × consumption × price per litre.
- New cars at German dealers carry a label with consumption, CO₂ and energy costs under the Pkw-EnVKV.
- Kilometres per litre is the reciprocal: 100 ÷ consumption.
Measuring your own consumption
The most reliable approach is the full-tank method:
- Fill up until the nozzle clicks off and note the odometer reading (or reset the trip meter).
- Drive normally, ideally until the tank is mostly empty again.
- Fill up again and read off the litres and the kilometres driven.
Consumption (l/100 km) = litres filled ÷ km driven × 100
Example: 42 litres after 600 km give 7 l/100 km. Averaged over several fill-ups, small differences in when the nozzle clicks off even out.
Calculate consumption from your fuel receipt
Enter litres filled and kilometres driven – consumption per 100 km appears instantly.
Working out fuel costs
Costs = km ÷ 100 × consumption (l/100 km) × price per litre
Example with an assumed price of €1.80 per litre: 600 km at 7 l/100 km use 42 litres and cost €75.60.
A holiday trip of 900 km then costs €113.40 – shared among 3 people, €37.80 each.
Calculate fuel costs
Enter distance, consumption and price per litre, optionally a return trip and splitting between passengers.
Commuting and tax
For the commute to work, what counts in a German tax return is not the fuel price but the commuting allowance of €0.38 per kilometre of one-way distance (Section 9 EStG).
Calculate the commuting allowance
Enter distance, working days and mode of transport – deductible work-related expenses.
Manufacturer figures and everyday driving
Anyone in Germany who displays or offers a new car must attach a label showing energy consumption, CO₂ emissions, energy costs, vehicle tax, CO₂ costs and CO₂ class (Section 3 Pkw-EnVKV). The figures come from the European type-approval procedure that Section 2 Pkw-EnVKV refers to via Regulation (EU) 2017/1151.
Why your own consumption differs
The test figure is produced in a fixed measuring cycle; your everyday driving – driving style, routes, load, weather – does not follow it. For your own cost calculations, the figure you measure yourself is therefore the most reliable.
Converting: km/l, mpg, kWh
Some countries calculate the other way round: how far you get on one unit of fuel. Kilometres per litre are 100 ÷ consumption – 7 l/100 km equal 14.29 km/l. For miles per gallon, use the converter.
Convert consumption
Convert between l/100 km, km/l and mpg (US and UK).
For electric cars, consumption is given in kWh per 100 km. The calculation is the same: kilometres ÷ 100 × consumption × electricity price per kWh.
Calculate charging costs for an EV
Enter consumption, electricity price and distance – with a comparison to a combustion car.
Frequently asked questions
How do I calculate consumption per 100 km?
How accurate is the trip computer?
How do I split fuel costs with passengers?
Sources
Every figure in this article comes from these primary sources or from the linked calculators, which are based on the same sources.
- Section 2 Pkw-EnVKV – definitions (test procedure) (accessed September 30, 2026)
- Section 3 Pkw-EnVKV – label at the point of sale (accessed September 30, 2026)
- Section 9 EStG – commuting allowance (accessed September 30, 2026)
Full-Stack Developer & Founder of HEADON.pro
Full-stack developer and founder of HEADON.pro. Developer of Rechnerzentrale.