Fuel Cost Calculator
Find how much fuel a trip needs and what it will cost, from the distance, your car’s fuel economy and the fuel price. It works in kilometres or miles, with fuel economy in L/100 km, km/L or miles per gallon (US or imperial), and can split the cost between passengers.
Result
Enter the distance, the fuel economy and the fuel price.
The calculation runs in this browser tab. Nothing you enter is uploaded, saved or logged.
How is the fuel cost of a trip calculated?
The cost is the amount of fuel the trip uses multiplied by the price of a unit of fuel. The fuel used is the distance times the fuel consumption. Consumption can be quoted in two opposite ways: as fuel per distance (litres per 100 km, where a smaller number is better) or as distance per fuel (km per litre, or miles per gallon, where a bigger number is better).
Miles per gallon also has two meanings, because the US gallon (3.785 litres) is smaller than the imperial gallon (4.546 litres) used in the United Kingdom. A car rated at 40 mpg in the UK uses less fuel per mile than one rated 40 mpg in the US. The calculator keeps the two apart and converts everything exactly to litres and kilometres.
How to use the Fuel Cost Calculator
- Enter the distance of the trip and choose kilometres or miles. For a round trip, choose “Round trip” and enter the one-way distance.
- Enter your fuel economy and its unit: L/100 km, km/L, mpg US or mpg UK.
- Enter the price of fuel and whether it is per litre, per US gallon or per imperial gallon.
- Optionally enter the number of people sharing the cost. Read the cost, the fuel needed and the cost per kilometre and per mile.
Formula
- Fuel needed
- litres = distance in km × (litres per 100 km) ÷ 100
- Cost
- cost = litres × price per litre
- From km/L
- L/100 km = 100 ÷ (km/L)
- From mpg
- L/100 km = 235.215 ÷ mpg (US) = 282.481 ÷ mpg (UK)
The constants come from the exact definitions: 235.215 = 100 × 3.785411784 ÷ 1.609344 for the US gallon, and 282.481 = 100 × 4.54609 ÷ 1.609344 for the imperial gallon.
A price per gallon is converted to a price per litre by dividing by the size of that gallon.
Worked example
A 320 km trip in a car that uses 6.5 L per 100 km, with fuel at 1.85 per litre, shared between 2 people. These are the results the calculator gives:
| Question | Result |
|---|---|
| Input: Trip distance | 320 |
| Input: Distance in | Kilometres |
| Input: Fuel economy | 6.5 |
| Input: Fuel economy in | Litres per 100 km (L/100 km) |
| Input: Fuel price | 1.85 |
| Input: Fuel price per | Litre |
| Input: Trip | One way |
| Input: People sharing the cost (optional) | 2 |
| Fuel cost | 38.48 |
| Distance driven | 320.00 km (198.84 mi) |
| Fuel needed | 20.80 L |
| Fuel needed, US gallons | ≈ 5.49 |
| Fuel needed, imperial gallons | ≈ 4.58 |
| Cost per kilometre | ≈ 0.1203 |
| Cost per mile | ≈ 0.1935 |
| Each of 2 people pays | 19.24 each |
Assumptions and limits
- The result is an estimate based on a single average fuel economy. Real consumption changes with speed, traffic, load, weather, tyre pressure and driving style, and is usually higher in town than on the motorway.
- The manufacturer’s official figure is measured under test conditions and is typically better than what most drivers achieve. Use the figure from your own tank fills if you have it.
- Only fuel is counted. Tolls, parking, wear and depreciation are not included.
- Cost is rounded to two decimals; the litres and per-distance figures are rounded and marked ≈ where they have more decimals than shown.
Frequently asked questions
How do I calculate the fuel cost of a trip?
Work out the litres used (distance in km × L/100 km ÷ 100), then multiply by the price per litre. For 320 km at 6.5 L/100 km that is 20.8 litres, and at 1.85 per litre it costs 38.48.
How do I convert mpg to L/100 km?
Divide 235.215 by the mpg figure for US gallons, or 282.481 by the mpg figure for imperial gallons. 30 mpg (US) is 7.84 L/100 km, and 30 mpg (UK) is 9.42 L/100 km.
What is the difference between US and UK mpg?
The imperial gallon is about 20% bigger than the US gallon, so the same car has a higher mpg number in the UK scale. A car at 33 mpg (US) is about 40 mpg (UK).
How do I find my car’s real fuel economy?
Fill the tank, reset the trip meter, drive normally, then fill up again. Divide the litres added by the distance driven and multiply by 100 to get L/100 km.
Is a lower L/100 km figure better?
Yes, it means less fuel per distance. For km/L and mpg the opposite is true: a higher figure is better.
How do I split the fuel cost between passengers?
Enter the number of people. The cost is shared to the cent, so that the shares add up to the total exactly; some people pay one cent more if it does not divide evenly.