Fuel Cost Calculator
Plan your trip budget with a precise fuel cost estimate. Enter your distance, vehicle fuel efficiency, and current fuel price to calculate the total cost and litres or gallons used. Switch between metric (km, L/100km, $/L) and imperial (miles, mpg, $/gallon) with a single click.
How It Works
Fuel cost calculations differ depending on whether you measure efficiency as litres per 100 kilometres (L/100km, used in most of the world) or miles per gallon (mpg, used primarily in the US and UK).
Metric Mode (L/100km):
Litres used = Distance (km) × Efficiency (L/100km) ÷ 100
Total cost = Litres used × Price per litre
Worked example: 500 km trip, 8 L/100km, $1.80/L
Litres = 500 × 8 ÷ 100 = 40 L
Cost = 40 × $1.80 = $72.00
Imperial Mode (mpg):
Gallons used = Distance (miles) ÷ Efficiency (mpg)
Total cost = Gallons used × Price per gallon
Worked example: 300 miles, 35 mpg, $3.50/gallon
Gallons = 300 ÷ 35 = 8.571 gallons
Cost = 8.571 × $3.50 = $30.00
Note on US vs UK gallons: The US gallon is 3.785 litres; the Imperial (UK) gallon is 4.546 litres. MPG figures for US vehicles and UK vehicles are not directly comparable — a UK car rated at 40 mpg (Imperial) is equivalent to about 33 US mpg. This calculator uses the unit you enter directly; ensure your efficiency and price figures use consistent gallon types.
Tips for accurate results:
Your vehicle's official fuel efficiency rating (from the manufacturer or government testing) is measured under controlled conditions and may be 10–20% optimistic compared to real-world driving, particularly in city traffic, with air conditioning, or in cold weather. For a realistic estimate, reduce your efficiency figure by 10–15% or use actual consumption data from past fill-ups.
Frequently Asked Questions
How do I find my car's fuel efficiency?
Check your vehicle's owner manual, the manufacturer's website, or government fuel economy databases (fueleconomy.gov for the US, Natural Resources Canada for Canada). For a real-world figure, divide the litres (or gallons) used on a recent fill-up by the distance driven since the previous fill-up.
What is the difference between L/100km and mpg?
L/100km measures how many litres of fuel are consumed per 100 kilometres driven — lower is more efficient. MPG measures how many miles you can travel per gallon — higher is more efficient. They are inversely related. To convert: L/100km = 235.21 ÷ mpg (US); mpg (US) = 235.21 ÷ L/100km.
Does this account for different fuel types (petrol vs diesel)?
The calculator is fuel-type agnostic — just enter your actual efficiency and fuel price, regardless of fuel type. Diesel vehicles typically achieve better efficiency (lower L/100km or higher mpg) than equivalent petrol vehicles, which you will see reflected in your efficiency figure.
How do I calculate cost per kilometre or mile?
Divide the total cost by the distance. For example, $72 for 500 km = $0.144 per km. You can use this to compare vehicle running costs or decide whether a trip is worth taking for a delivery or rideshare job.
Why does my actual fuel cost differ from the estimate?
Real-world fuel consumption varies with driving style, speed, road type (highway vs city), cargo weight, weather, and vehicle condition. Manufacturer-rated efficiency is often measured under optimal conditions. For best accuracy, use consumption data from your last 2–3 full fill-ups.