Fuel Cost Calculator
Estimate trip fuel cost and split it by passenger — supports l/100km, mpg US, mpg UK, and km/l.
All efficiency units
Works with l/100km, mpg US, mpg UK, and km/l — including round trips.
Estimate only
Real consumption varies with load, traffic, speed, and air conditioning.
What does this calculator do?
Trip fuel cost and per-person split in seconds
Enter your trip distance, vehicle fuel efficiency, and current pump price to see the total fuel cost and how it splits between passengers. The calculator works with any efficiency unit — l/100km common in Europe, mpg in the US and UK, or km/l used in parts of Asia and Latin America.
The formula is straightforward: multiply distance by consumption to get fuel volume, then multiply by price.
Fuel (l) = Distance (km) × Consumption (l/100km) ÷ 100
Cost = Fuel (l) × Price per litre
Cost per person = Cost ÷ PassengersThe cost per 100 km is simply price per litre multiplied by consumption in l/100km — a useful figure for comparing routes or vehicles.
This is the key insight most fuel-cost tools miss: mpg and l/100km are inversely related, not linearly. You cannot convert by multiplying or dividing by a fixed factor.
l/100km = 235.215 ÷ mpg (US)
l/100km = 282.481 ÷ mpg (UK)
mpg (US) = 235.215 ÷ l/100kmThe constants come from official unit definitions:
- 1 US gallon = 3.785411784 litres (NIST SP 811, exact)
- 1 UK (imperial) gallon = 4.54609 litres (UK Weights and Measures Act 1985, exact)
- 1 international mile = 1.609344 km (1959 international yard and pound agreement, exact)
US mpg constant: 100 × 3.785411784 ÷ 1.609344 ≈ 235.215
UK mpg constant: 100 × 4.54609 ÷ 1.609344 ≈ 282.481
A 30 mpg US car gets worse efficiency in l/100km than a 30 mpg UK car, because UK gallons are about 20 % larger.
A family drives from Berlin to Hamburg (289 km) and back (round trip = 578 km). The car consumes 8.5 l/100km. Diesel costs €1.65/l. There are 4 people in the car.
Apply round-trip multiplier
578 km (289 × 2) is the total distance.
Calculate fuel needed
578 km × 8.5 l/100km ÷ 100 = 49.13 l
Calculate total cost
49.13 l × €1.65/l = €81.07
Split by passenger
€81.07 ÷ 4 = €20.27 per person
The US Department of Energy's fueleconomy.gov identifies these factors as the most impactful:
Steady highway speed
Fuel economy typically peaks at 80–90 km/h (50–55 mph) and drops steeply above 110 km/h (70 mph). Cruise control helps maintain an efficient speed.
Reduce air conditioning use
AC can increase fuel consumption by up to 25 % in stop-and-go traffic. At highway speeds, open windows increase drag — AC is often the better choice.
Reduce unnecessary weight
An extra 45 kg (100 lbs) reduces fuel economy by roughly 1–2 %. Remove roof racks and cargo carriers when not in use.
Tyre pressure and vehicle maintenance (air filter, engine oil) also affect real-world consumption. The ADAC (German automobile club) publishes real-world consumption data for hundreds of vehicles that is typically 20–30 % higher than manufacturer figures.
The total cost is the fuel cost only. It does not include tolls, parking, vehicle wear, or driver time. For a rough total trip cost, add €0.02–0.04/km for vehicle depreciation and maintenance.
The cost-per-person figure is calculated by dividing the total fuel cost evenly — it does not account for different distances driven by different passengers.
The cost per 100 km is the most useful figure for comparing routes (different distances) or vehicles (different efficiency). It is independent of trip length.
A useful benchmark for judging your own number: according to the U.S. Department of Energy's fueleconomy.gov guidelines, aggressive driving alone can raise fuel use by 10–40 % in stop-and-go traffic, so a per-100-km cost noticeably above your car's spec sheet usually points at driving conditions before it points at the car. According to ADAC's fuel-saving guidance, anticipatory driving and correct tire pressure are the two cheapest levers — together they routinely recover 10–15 % of the costs this calculator shows you.
If you split costs with passengers regularly (commuting groups, festival trips), agree on the basis up front: fuel-only, as calculated here, or fuel plus a per-kilometer wear surcharge. The fuel-only figure is the defensible minimum; the all-in figure is fairer to the driver.
Real fuel consumption depends on many factors this calculator cannot know.
Actual consumption varies significantly
Manufacturer consumption figures and most online estimates are under ideal conditions. Traffic congestion, hills, high speed, air conditioning, passenger load, and cold weather all increase real consumption — sometimes by 30–50 % versus the manual specification. Use your actual fuel history for best accuracy.
Price volatility
Fuel prices change daily. The result reflects the price you enter and may be out of date within hours at times of market volatility. Check current prices at a site like the ADAC fuel price monitor or GasBuddy before a long trip.
These results are for informational purposes only. If you reclaim trip costs as a business expense or commuter allowance, verify the applicable tax requirements first — flat per-kilometer rates (such as the German Pendlerpauschale or the IRS standard mileage rate) usually replace, not supplement, the actual fuel cost calculated here, and a tax professional can tell you which basis applies to your situation.