How to Calculate Fuel Cost for a Trip
5 min read · Updated September 26, 2026 · by the SolveCalcPro editorial team
Trip fuel cost is distance divided by efficiency, times price. The only complication is that efficiency comes in different units. This guide shows the conversions.
The basic calculation
Fuel = distance ÷ km per litre; cost = fuel × price. A 300 km round trip (600 km) at 15 km/l uses 40 litres (10.57 US gal · 8.799 UK gal); at ₹100 a litre it costs ₹4,000.00 — ₹2,000.00 each for two people.
Converting efficiency units
- L/100 km = 100 ÷ km/l (15 km/l = 6.67 L/100 km).
- US mpg × 0.4251 = km/l; UK mpg × 0.3540 = km/l.
- 1 US gallon = 3.785 L; 1 UK gallon = 4.546 L.
CO₂ estimate
The U.S. EPA uses 8,887 g of CO₂ per US gallon of gasoline and 10,180 g per gallon of diesel — about 2.35 kg and 2.69 kg per litre.
Getting realistic
Use real-world efficiency, not the brochure figure, and add tolls and parking. The fuel cost calculator handles all the units.
Practice questions
Test yourself, then tap to check. Answers are calculated by the tools linked below.
- A 450 km one-way trip at 18 km/l with petrol at ₹105 a litre. What is the fuel cost?
Show answer
Total fuel cost: ₹2,625.00
- A train travels 420 km in 3.5 hours. What is its speed?
Show answer
Speed: 120 km/h
- A recipe needs 3 cups of milk. How many millilitres?
Show answer
3 cup in mL: 709.7647095
Frequently asked questions
How do I calculate fuel cost?
Divide the distance by your efficiency to get the fuel, then multiply by the fuel price.
How do I convert mpg to L/100 km?
Divide 235.2 by US mpg (or 282.5 by UK mpg).
Is brochure mileage reliable?
Usually optimistic; real-world figures are lower.
How do I split fuel costs?
Divide the total by the number of people sharing.
Try it yourself
Fuel Cost CalculatorWork out the fuel needed and cost for a trip in km or miles, with km/l, L/100 km or mpg, split between people.Speed, Distance and Time CalculatorFind speed, distance or travel time from the other two, with km, miles, minutes and hours.
Volume ConverterConvert litres, millilitres, US gallons, quarts, pints, cups and fluid ounces for cooking and fuel.Keep learning
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