What is gas mileage?
Gas mileage (fuel economy) describes the relationship between the distance traveled and the amount of fuel burned. Your actual fuel consumption depends on many factors, including your vehicle model, engine size, driving style, tire pressure, traffic, weather, and payload.
Knowing your fuel economy is useful not only for comparing vehicles, but also for planning trips and estimating how much fuel (and money) you’ll need before you set off.
How to use the MPG calculator
This MPG calculator helps you calculate fuel efficiency and fuel usage in both measurement systems:
- American system: miles, gallons (US or UK), and MPG.
- Metric system: kilometers, liters, and liters per 100 km (L/100km).
Choose whether you know your fuel economy (MPG or L/100km) or your fuel used (gallons or liters). Enter the trip distance, and the calculator will compute the missing values and show equivalent fuel-economy units (MPG US, MPG UK, and L/100km).
Fuel price and trip cost
If you also enter a fuel price, the calculator estimates your total trip cost. You can choose from multiple world currencies so you can see results in your local currency.
Formulas
American system
- MPG = Distance (miles) ÷ Fuel used (gallons)
- Fuel used (gallons) = Distance (miles) ÷ MPG
Metric system
- L/100km = Fuel used (liters) ÷ Distance (km) × 100
- Fuel used (liters) = Distance (km) × (L/100km) ÷ 100
FAQs
How do I calculate MPG?
- Record how many miles the car travels.
- Measure how many gallons of fuel were used.
- Divide miles by gallons.
- The result is your MPG for that trip.
How many gallons does my car hold?
Many passenger cars hold roughly 12–16 gallons, depending on the vehicle size. Your owner’s manual is the best place to check the exact capacity.
What affects MPG?
- Fast acceleration, hard braking, and high speeds
- Cold weather and short trips (engine not at optimal temperature)
- Extra weight (cargo, roof racks) and towing
- Air conditioning use
- All-wheel-drive vs. two-wheel-drive operation