Fuel Cost Calculator
How much will you spend on fuel for a trip? Enter the distance, your car’s average consumption (in litres per 100 km) and the current fuel price, and the calculator shows the litres needed, the total cost, the cost per kilometre and, if you share the car, the cost per person. You can count the trip one way or there and back.
Enter the distance, your car’s consumption in litres per 100 km and the price per litre. For example, 100 km at 6 l/100 km and €1.80/l costs €10.80.
Educational estimate, not financial advice. It estimates only the fuel cost; it does not include tolls, wear, servicing, insurance or the annual vehicle tax.
The fuel cost sum
The calculation is a simple multiplication. First, the litres you will use: distance divided by 100, times the consumption in litres per 100 km. Then the cost: those litres times the price per litre. For example, 100 km in a car that does 6 l/100 km uses 6 litres; at €1.80 a litre, that is €10.80 of fuel.
Your car’s consumption (l/100 km)
The average consumption is the number that most affects the result. It is on the car’s spec sheet (combined WLTP consumption), but real consumption depends on driving style, speed, traffic and load. For a reliable estimate, use the figure you usually see on the trip computer rather than the catalogue value, which is almost always optimistic.
The fuel price
The price per litre changes almost every day and varies between stations and between petrol and diesel. Use the current price of the fuel your car takes. In Portugal you can check the daily average price on the DGEG fuel-price portal. Because the price is a value you enter, this calculator does not rely on any table that goes stale.
Round trip, cost per km and splitting
If you tick “round trip”, the calculator doubles the distance before everything else. The cost per kilometre (total cost divided by distance) helps you compare routes and see the cost of every kilometre you drive. And if you carpool, the number-of-people field splits the total cost between everyone, showing how much each person pays.
Worked example
Picture a trip from Lisbon to Porto, about 313 km, in a car that does 5.5 l/100 km, with diesel at €1.75 a litre. One way uses about 17.2 litres, that is €30.13. There and back (626 km) is 34.43 litres and €60.25. If you split the round trip between two people, it comes to €30.13 each, barely more than a one-way trip on your own.
Frequently asked questions
How do you calculate the fuel cost of a trip?
What is consumption in litres per 100 km?
How much does it cost to drive 100 km?
Does the result include tolls, wear or insurance?
Should I use the catalogue consumption or the real one?
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Sources
- Preços de combustíveis (preço médio diário) — Direção-Geral de Energia e Geologia (DGEG)
- Etiquetagem e consumo de combustível dos veículos — Automóvel Club de Portugal (ACP)
Author: Thorben Rasmus Idel · Reviewed by: Nahar Geva · Last reviewed: 2026-06-26