Fuel Cost Calculator
Estimate what a journey will cost in fuel. Enter distance, your car efficiency in any common unit and the fuel price, then split the bill between passengers.
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How to use Fuel Cost Calculator
- Enter the trip distance in kilometres or miles.
- Enter your fuel efficiency and choose km/L, L/100km, mpg (US) or mpg (UK).
- Enter the fuel price and whether it is per litre, US gallon or UK gallon.
- Set the number of passengers to see each share, or use the converter card to switch efficiency units.
The formulas
Everything is converted to litres per kilometre first. From km/L that is 1 ÷ x; from L/100km it is x ÷ 100; from US mpg it is 3.785411784 ÷ (1.609344 × x); and from UK mpg it is 4.54609 ÷ (1.609344 × x). Then fuel used = distance in km × litres per km, and trip cost = fuel used × price per litre. Prices per gallon are divided by the matching gallon size in litres.
Worked example: a 250 km trip in a car using 7.5 L/100km needs 250 × 0.075 = 18.75 litres. At 1.80 per litre the cost is 18.75 × 1.80 = 33.75, or 0.135 per km. Split between four people, each pays 8.44 after rounding.
Ways to spend less on fuel
- Keep tyres inflated to the pressure recommended for your vehicle.
- Drive smoothly: heavy acceleration and braking increase consumption.
- Remove roof racks and unneeded weight when not in use.
- Share rides for regular commutes and long trips.
- Plan routes to avoid heavy traffic and unnecessary detours.
What this tool does not include
The calculator covers fuel only. Tolls, parking, maintenance, insurance and depreciation are separate costs, and electric vehicles use kilowatt-hours rather than litres. Currency is whatever your price is in; the tool performs no currency conversion. Treat the result as a planning estimate, not a guaranteed figure. A useful habit is to note the fuel used and distance at each fill-up and compute your own real-world efficiency; that measured number is almost always more honest than the brochure figure, because it reflects your roads, loads and driving. Enter it in the tool for a trustworthy trip budget. All inputs stay in your browser.
Why use this fuel cost calculator tool
- Four efficiency units. km/L, L/100km, US mpg and UK mpg, with accurate gallon definitions.
- Full trip breakdown. Total cost, fuel needed, cost per km and per mile.
- Cost splitting. Divide the fuel bill fairly between everyone in the car.
- Efficiency converter. Convert any efficiency value into all four units at once.
Frequently asked questions
Why do US and UK mpg differ?
The UK (imperial) gallon is 4.54609 litres while the US gallon is 3.785411784 litres, so the same car shows a higher number in UK mpg. For instance, 30 US mpg is about 36 UK mpg. Always check which gallon a figure uses.
How do I convert mpg to L/100km?
For US mpg, divide 235.215 by the mpg figure; for UK mpg, divide 282.481. So 30 US mpg is 235.215 ÷ 30, about 7.84 L/100km. Notice that a higher mpg is better but a lower L/100km is better.
Is the cost exact?
No, it is an estimate. Real consumption depends on speed, load, traffic, terrain, tyre pressure, air conditioning and driving style, and prices change by station. Use the official or measured efficiency of your own vehicle for the best result.
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