Fuel Cost Calculator
Estimate the fuel needed, total cost and cost per kilometer or mile for a trip from distance, your vehicle's mileage and the fuel price.
The formula
Fuel needed = Distance ÷ Mileage. Cost = Fuel needed × Price per unit of fuel. Cost per kilometer (or mile) = Price ÷ Mileage. For a round trip the distance you enter is doubled before the fuel is worked out.
Worked example
A 300 km trip in a vehicle averaging 15 km/liter needs 300 ÷ 15 = 20 liters. At 100 per liter, that's an estimated cost of 2,000, which is 100 ÷ 15 = 6.667 per km.
A round-trip example
Enter 120 km, choose Round trip, 12 km per liter and a price of 1.60 a liter. The distance driven is 240 km, which needs 240 ÷ 12 = 20 liters and costs 20 × 1.60 = 32.00. Dividing the price by the mileage gives the cost per kilometer, 1.60 ÷ 12, shown as 0.133.
US and UK examples
US units: a 150-mile trip each way is 300 miles. At 25 MPG that needs 12.00 US gallons, and at 3.50 per gallon it costs 42.00, or 0.140 per mile. UK units: 400 miles at 45 MPG (UK) needs 8.89 imperial gallons, and at 6.60 per imperial gallon it costs 58.67, or 0.147 per mile.
A UK gallon is 4.54609 liters and a US gallon is 3.785411784 liters, so MPG figures from the two countries are not interchangeable. UK pump prices are usually quoted per liter; multiply by 4.54609 to get the price per imperial gallon that the UK setting expects.
If your car's figure is in mpg or L/100 km
In metric mode the mileage box wants kilometers per liter. For a figure in liters per 100 km, divide 100 by it to get km/L. A figure in US miles per gallon converts as km/L = mpg × 0.425144, so 30 mpg is about 12.75 km/L, which is also about 7.84 L/100 km. The Fuel Economy Converter does these conversions for you, and the Fuel Average Calculator works out your own figure from a tank of fuel.
Why real fuel use varies
- Higher speeds, stop-and-go traffic, hills, extra load, air conditioning and under-inflated tires all raise consumption.
- Your own tracked figure from a full tank to the next one is usually more reliable than the manufacturer's number.
Units and what the boxes expect
- Metric uses kilometers, kilometers per liter and a price per liter. US uses miles, US MPG and a price per US gallon. UK uses miles, UK MPG and a price per imperial gallon. Changing the units does not convert the numbers already typed in, so re-enter them.
- With One way selected the distance is used as entered. With Round trip it is doubled, and the results then show the total distance driven.
- Fuel is shown to two decimals followed by its unit, even for tiny amounts: 1 km at 15 km/L is 0.07 liters.
- Cost per kilometer or mile is shown to three decimals, because it is often a small number.
- A price of 0 is accepted and gives a cost of 0.00. Distance and mileage must be above zero, and a negative price is rejected.
More worked examples
450 km at 18 km/L with fuel at 96.50 needs 25.00 liters and costs 2412.50. 800 km at 12.5 km/L with fuel at 1.45 needs 64.00 liters and costs 92.80. A short 12 km trip at 8.4 km/L with fuel at 1.80 needs 1.43 liters and costs 2.57.
What it leaves out
It prices only the fuel you enter. Tolls, parking and a change in fuel price during the trip are not included, and the cost has no currency symbol or thousands separator.
Frequently asked questions
Where do I find my vehicle's mileage?
Your vehicle's manual or dashboard trip computer usually gives an average figure. For a more accurate result, calculate your own real-world mileage by tracking fuel used over a known distance.
Does this account for traffic, terrain, or driving style?
No — it assumes your mileage figure already reflects typical driving conditions. Highway driving is usually more efficient than stop-and-go city traffic, so adjust the mileage input if your trip is unusual.
How do I calculate a round trip?
Enter the one-way distance and set Trip type to Round trip. The calculator doubles it: 120 km one way at 12 km/L needs 20 liters, while the same entry as One way gives 10.
Can I enter miles and miles per gallon?
Yes. Choose US or UK in the Units box. US uses miles, US MPG and a price per US gallon; UK uses miles, imperial MPG and a price per imperial gallon. Pick the gallon your MPG figure was measured in, because an imperial gallon is about 20% larger.