Gas Mileage Calculator: Improve Your Fuel Savings

A gas mileage calculator provides information specific to your vehicle’s fuel performance based on the data you input. The information output — like miles per gallon (mpg) or annual fuel cost — can help you plan and make decisions in different ways.

• When you have an estimate of your annual fuel costs, you can build that into your weekly or monthly budget.

• If your car’s actual mpg is lower than expected, it might indicate a mechanical problem that needs correcting to reduce gas consumption.

• If you’re thinking of buying a different car, a gas calculator can compare expected gas expenses for other cars with what you’re currently spending.

NerdWallet’s gas calculator is a simple-to-use tool broken into two parts: step one calculates your car’s mpg and step two shows your annual fuel expenses compared to another vehicle’s estimated mpg.

To make using the gas calculator easier, gather and document information ahead of time. For step one, you’ll need to input the following:

• Note your car’s odometer reading after you fill up the gas tank, then note the odometer reading the next time you fill up. These odometer readings are used to determine how many miles you got on one full gas tank, so you’ll want to make sure your tank is as empty as possible before the second fill-up.

• How many gallons of gas you needed to fill your tank the second time.

You may want to complete these steps several times to get an average mpg, since your driving habits can change between fill-ups. For example, you might do more highway driving during one cycle, which consumes less gas than city driving.

For step two, you will need the following:

• The average price you pay for a gallon of gasoline. You can also find average gas prices on NerdWallet’s website.

• An estimate of the number of miles you drive each year. According to the U.S. Department of Transportation’s Federal Highway Administration (FHWA), the average person drives about 13,500 miles per year. 

• If you want to compare your current car’s fuel costs with another vehicle, you’ll need the other car’s estimated mpg. You can find this estimate for most vehicles at fueleconomy.gov.