## Determining a Car’s Fuel Efficiency

This calculator can be used to figure out a car’s fuel efficiency as well as the cost of fuel per mile (or kilometer), monthly, and annual costs too. The calculator needs a total of six inputs, including:

- Whether the calculator should use US Customary or Metric units of measure
- The vehicle’s initial odometer reading, which would be the reading on the odometer after fueling up
- The vehicle’s final odometer reading, which would be the odometer reading at the next refueling after the initial reading
- The volume of fuel (gasoline, diesel, petrol) consumed in gallons or liters between the initial and final odometer readings
- The cost of fuel per gallon or liter
- An estimate of the total number of miles, or kilometers, driven each year

The calculator then provides the user with five outputs:

- The number of miles, or kilometers, driven based on the initial and final odometer reads
- The fuel efficiency of the car, stated in terms of either miles per gallon (MPG) or liters per 100 kilometers
- The cost to drive the car per mile or kilometer
- The monthly and yearly fuel cost to drive the vehicle

### Fuel Economy as Measured by Miles Per Gallon (MPG) and Liters per 100 Kilometers

While it may seem like common sense to some, if no one’s ever explained to you how to measure the fuel efficiency of your car, truck, or SUV, it might not be so obvious. Typically, drivers want to understand their vehicle’s highway fuel efficiency value since driving around town, which can mean of lot of idling, can be far less insightful. In practice, there are only a few steps you need to follow to capture the information needed to perform this calculation:

- The most accurate way to measure a car’s highway performance is by fueling up the vehicle before taking a long trip on a highway. You’ll want to make sure the fuel tank is full, and you will want to take an odometer reading. This will be the Initial Odometer Reading used by this calculator.
- Once that road trip is over, you’ll want to refuel the car. Once again, you want to make sure the fuel tank is completely full and you need to make note of two things.
- The car’s odometer reading, which will be used as this calculator’s Final Odometer Reading. Knowing both the Initial and Final Odometer reading allows us to calculate the distance driven between the two refueling events.
- The gallons, or liters, of fuel used to fill up the car. This value will be input as the Fuel Used value. Since the car started with a full tank and the tank was filled up again after the trip, we know exactly how much fuel was consumed during the trip

- Finally, you’ll also want to make note of the fuel cost per gallon or liter. Knowing this value allows us to calculate the Cost per Mile or Kilometer as well as the fuel Cost per Month and Cost per Year.

Write all these numbers down or take a picture of the readings and bring them back here to crunch through the numbers. Of course, you can use the same approach to figure out the average fuel economy for your car too. Just fill up the tank, make note of the odometer reading, drive around until the tank’s nearly empty, fill up the tank again and note the odometer reading and fuel consumed. It really is that simple.