Fuel Cost Calculator
Work out the gas or petrol cost of any journey from your distance, fuel efficiency, and fuel price — with support for mpg, km/L, and L/100km, a round-trip toggle, and your own currency.
Frequently Asked Questions
Does it support both mpg and L/100km?
Yes. You can choose US miles per gallon, kilometres per litre, or litres per 100 km, and the calculator converts your distance and price to the matching unit system automatically.
Can it calculate a round trip?
Yes. Turn on the round-trip toggle and the calculator doubles your entered distance before working out the fuel volume and total cost.
What currency does it use?
It uses whichever currency you have selected for the site, so the total cost, fuel price, and cost-per-distance all display in your chosen currency.
Understanding the Fuel Cost Calculator
The Fuel Cost Calculator estimates what a trip costs in gas or petrol, entirely in your browser. Enter your distance in kilometres or miles, your vehicle's fuel efficiency, and the current price of fuel, and it returns the total fuel needed, the total cost, and the cost per kilometre or mile. It understands three common efficiency conventions — litres per 100 km, kilometres per litre, and US miles per gallon — and asks for the fuel price in the matching unit (per litre or per gallon). A round-trip toggle doubles the distance for there-and-back journeys, and every money figure displays in your selected site currency.
How it works
You pick a distance unit, an efficiency convention, and type in three numbers: distance, efficiency, and fuel price. The tool first applies the round-trip toggle, then converts your distance to the unit the chosen convention expects. For litres per 100 km it computes volume as distance in km divided by 100, times the figure. For km per litre it divides distance in km by the figure. For US mpg it divides distance in miles by the figure to get gallons. Total cost is fuel volume multiplied by price, and cost per distance is total cost divided by the trip distance. Inputs must be positive, or a friendly message appears.
Worked example
Suppose you drive 120 km, your car uses 7.5 litres per 100 km, and petrol costs 1.60 per litre. Fuel needed is 120 / 100 x 7.5 = 9.00 litres, so the trip costs 9.00 x 1.60 = 14.40, or 0.120 per km. Switching to US units for a 100-mile each-way commute at 25 mpg and 3.50 per gallon, with round trip enabled, the distance becomes 200 miles, fuel needed is 8.00 gallons, and the total is 28.00, or 0.140 per mile.
Tips & common mistakes
- Pick the efficiency convention your car's display uses — L/100km and km/L are common outside North America, while mpg (US) is standard in the United States.
- Remember US mpg differs from imperial (UK) mpg; this tool uses US gallons, so convert imperial figures before entering them.
- Enter the fuel price in the unit the calculator asks for — per litre for the metric modes, per gallon for mpg.
- Use the round-trip toggle for commutes and return journeys so you do not have to double the distance by hand.
- Real-world efficiency varies widely — highway driving is typically 20–30% more efficient than stop-start city traffic, so use a conservative figure for trip budgeting and nudge it down further for cold weather, hills, or a loaded vehicle.
- Fuel prices and taxes vary a lot by region and over the year, so use the current local price for the most accurate estimate, and set your preferred currency with the site's selector before calculating.