Fuel Cost Calculator
Work out how much a trip will cost in fuel, one-way or round trip, in miles or kilometers — and optionally compare it against a second vehicle.
How to Calculate Fuel Cost for a Trip
- Choose your preferred units — Miles/Gallon or Liters/100km — using the toggle pills.
- Enter your trip distance, your vehicle's fuel efficiency, and the price per gallon (or liter).
- Check "Round trip" if the distance you entered is one-way and you want the cost for the full there-and-back trip.
- Optionally enter a second vehicle's fuel efficiency to compare its cost for the exact same trip.
- Click "Calculate" to see the fuel needed, total fuel cost, cost per mile or kilometer, and — if you filled it in — how much a second vehicle would cost and save.
Frequently Asked Questions
How does the calculation differ between MPG and L/100km modes?
In MPG mode, fuel needed is distance divided by MPG, since MPG expresses distance per unit of fuel; in L/100km mode, fuel needed is distance divided by 100 and multiplied by the L/100km figure, since that metric expresses fuel used per 100 km rather than distance per unit of fuel — the tool switches formulas automatically when you toggle units.
Where do I find my vehicle's fuel efficiency number?
Check your car's manual, window sticker for a new vehicle, or manufacturer's spec sheet for its official MPG or L/100km rating — real-world efficiency can vary with driving style, terrain, and vehicle load, so treat the built-in rating as an estimate.
Does this calculator account for fuel price changes during a long trip?
No — it assumes a single, constant price per gallon or liter for the entire trip; if prices vary significantly along your route, the actual total cost may differ from the estimate.
What's the difference between Total Fuel Cost and Cost per Mile?
Total Fuel Cost is the full dollar amount for the whole trip, while Cost per Mile (or per km) divides that total by the distance, which is useful for comparing trip costs on a per-unit-distance basis regardless of total distance.
Can I use this for costs other than gasoline, like diesel or electric charging?
Yes, as long as you enter the correct price per unit and your vehicle's efficiency in the matching unit — the math itself doesn't care what fuel type it represents, it's simply distance, efficiency, and price.
How does the Round Trip checkbox work?
It simply doubles whatever distance you entered before running the calculation — so if you typed in the one-way mileage, checking it gives you the fuel needed and cost for the full there-and-back trip instead of just one leg.
How does comparing a second vehicle work?
Enter a second fuel efficiency figure in the same unit (MPG or L/100km) as your main vehicle, and the calculator runs the exact same distance and fuel price through that efficiency to show Vehicle B's total cost and how much more or less it would cost for the identical trip — useful for comparing two cars before a purchase or road trip.