AUTO CALCULATOR
Gas Mileage Calculator
Calculate your vehicle's gas mileage and fuel economy using the distance you traveled and the amount of fuel you used.
Enter the distance you actually drove and the amount of fuel used during the trip.
What Is Gas Mileage?
Gas mileage measures how efficiently a vehicle uses fuel. In the United States, fuel economy is commonly expressed as miles per gallon (MPG).
A higher MPG means the vehicle can travel more miles using the same amount of fuel.
How to Calculate Gas Mileage
To calculate MPG, divide the number of miles driven by the number of gallons of fuel used.
MPG = miles driven ÷ gallons of fuel used
For example, if you drive 300 miles and use 12 gallons of gasoline:
300 ÷ 12 = 25 MPG
Your vehicle's estimated fuel economy would therefore be 25 miles per gallon.
How to Calculate L/100 km
Liters per 100 kilometers (L/100 km) is a common fuel-consumption measurement outside the United States.
Unlike MPG, a lower L/100 km value indicates better fuel efficiency because the vehicle uses less fuel to travel the same distance.
MPG to L/100 km
MPG and L/100 km measure fuel economy differently. MPG measures distance traveled per unit of fuel, while L/100 km measures fuel used over a fixed distance.
To convert MPG to L/100 km:
L/100 km = 235.215 ÷ MPG
For example, 25 MPG is approximately 9.41 L/100 km.
Gas Mileage Example
Suppose you reset your vehicle's trip odometer after filling the fuel tank. You drive 350 miles before filling up again and the vehicle requires 14 gallons of fuel.
The gas mileage is:
350 ÷ 14 = 25 MPG
This means the vehicle traveled approximately 25 miles for every gallon of fuel used.
What Affects Gas Mileage?
Actual fuel economy can vary depending on how and where a vehicle is driven. Factors that can affect gas mileage include:
- Driving speed
- Acceleration and braking habits
- Traffic conditions
- Vehicle weight
- Tire pressure
- Weather conditions
- Road conditions
- Air conditioning use
How to Get More Accurate Gas Mileage
For a more reliable estimate, record the distance driven and the fuel added over several fill-ups rather than relying on a single trip.
Using the same measurement method over multiple tanks can help reduce the effect of small differences in fuel level and driving conditions.
Gas Mileage vs. Fuel Cost
Gas mileage tells you how efficiently your vehicle uses fuel, while fuel cost tells you how much money you spend on that fuel.
You can use our Fuel Cost Calculator to estimate the cost of a trip based on distance, fuel efficiency, and fuel price.
Frequently Asked Questions
How do I calculate my car's MPG?
Divide the number of miles you drove by the number of gallons of fuel used. For example, 300 miles divided by 12 gallons equals 25 MPG.
Is higher MPG better?
Generally, yes. A higher MPG means the vehicle can travel farther using the same amount of fuel.
Is lower L/100 km better?
Yes. A lower L/100 km value means the vehicle uses less fuel to travel 100 kilometers.
What is good gas mileage?
What counts as good gas mileage depends on the vehicle type, drivetrain, engine, driving conditions, and other factors. Comparing your actual fuel economy with the manufacturer's rating can be more useful than using one universal MPG target.
How can I improve my gas mileage?
Maintaining proper tire pressure, avoiding unnecessary aggressive acceleration, reducing unnecessary weight, and maintaining the vehicle properly can help improve fuel efficiency.
How accurate is the gas mileage calculator?
The calculator uses the distance and fuel amount you provide. The result is mathematically based on those inputs, but real-world fuel economy can vary because driving conditions and fuel measurements are not always exact.