Gas Mileage Calculator by Make and Model

This calculator estimates your vehicle’s gas mileage (miles per gallon or liters per 100 km) based on the make and model you select, using typical EPA-rated fuel economy data. You enter your car’s make and model, choose the year, and the calculator returns the combined city/highway MPG, annual fuel cost, and CO2 emissions. It helps you compare vehicles or check if your real-world mileage matches the official rating.

Formula

The calculator uses the EPA’s combined fuel economy formula, which is a weighted average of city (55%) and highway (45%) MPG values. For a given vehicle, the combined MPG is calculated as:

Combined MPG = 1 / (0.55 / City MPG + 0.45 / Highway MPG)

Where:

• City MPG – miles per gallon in stop-and-go city driving (lower speed, frequent braking).
• Highway MPG – miles per gallon in steady highway driving (higher speed, less braking).

For the annual fuel cost, the formula is:

Annual Fuel Cost = (Annual Miles / Combined MPG) × Price per Gallon

Where Annual Miles is assumed to be 12,000 miles (a common EPA assumption), and Price per Gallon is the average fuel price you enter (default $3.50).

For CO2 emissions, the EPA uses a factor of 8,887 grams of CO2 per gallon of gasoline burned. So:

CO2 (g/mile) = 8,887 / Combined MPG

Worked Example

Using the default inputs: Make = Toyota, Model = Corolla, Year = 2021, and a fuel price of $3.50 per gallon.

Assume the 2021 Toyota Corolla has an EPA rating of 30 MPG city and 38 MPG highway. First, calculate the combined MPG:

1. City portion: 0.55 / 30 = 0.01833
2. Highway portion: 0.45 / 38 = 0.01184
3. Sum: 0.01833 + 0.01184 = 0.03017
4. Combined MPG = 1 / 0.03017 = 33.1 MPG (rounded to 33)

Next, annual fuel cost: (12,000 / 33.1) × $3.50 = 362.5 gallons × $3.50 = $1,268.75 (rounded to $1,269).

CO2 emissions: 8,887 / 33.1 = 268.5 g/mile (rounded to 269).

The calculator outputs these values: Combined MPG = 33, Annual Fuel Cost = $1,269, CO2 = 269 g/mile.

How to Choose a Vehicle Based on Gas Mileage

When comparing vehicles, look at the combined MPG as a single number that represents typical driving. However, consider your own driving patterns:

• If you do mostly city driving, focus on the city MPG rating.
• If you do mostly highway driving, focus on the highway MPG rating.
• For a mix, the combined rating is a good baseline.

Also, note that the EPA ratings are based on standardized tests, so real-world mileage may vary by 10-20% depending on driving style, terrain, and vehicle condition.

Common Mistakes When Calculating Gas Mileage

One common mistake is mixing up units. Some countries use liters per 100 km (L/100km) instead of MPG. To convert MPG to L/100km, use the formula: L/100km = 235.215 / MPG. For example, 30 MPG equals 7.84 L/100km.

Another mistake is using the wrong annual mileage. The EPA assumes 12,000 miles per year, but if you drive more or less, adjust the formula accordingly.

Finally, don’t use the combined MPG for a specific trip; it’s an average, not a precise prediction.

Real-World vs. EPA Ratings

Many drivers find their actual mileage is lower than the EPA rating, especially in cold weather, with heavy loads, or with aggressive driving. The EPA tests are done in a lab with controlled conditions, so they don’t account for traffic, hills, or wind. To get a more accurate estimate for your driving, track your own mileage over a few tanks of gas.

Alternatives to the Calculator

If you want more detailed data, the U.S. Department of Energy’s fueleconomy.gov website provides official EPA ratings for all vehicles, including historical data. You can also use smartphone apps that track your real-world mileage. For a quick estimate, this calculator gives you a good starting point.

Frequently Asked Questions

How accurate is the calculator?

The calculator uses EPA combined MPG ratings, which are based on standardized tests. Real-world mileage can vary by 10-20% due to driving conditions, so treat the result as an estimate, not a guarantee.

Can I use this for electric vehicles?

No, this calculator is for gasoline-powered vehicles. For EVs, you’d use MPGe (miles per gallon equivalent) and electricity costs instead.

Why does my car get lower MPG than the rating?

Common reasons include: driving at high speeds, rapid acceleration, carrying heavy loads, using air conditioning, and cold weather. Also, if your car is older or poorly maintained, fuel economy can drop.

How do I calculate my own gas mileage?

Fill your tank completely, note the odometer reading, drive until you need to refill, then fill again and note the gallons used. Divide the miles driven by the gallons used to get your MPG.

What is a good MPG for a new car?

For a new car, a combined MPG of 30 or higher is considered good. Compact cars and hybrids often exceed 40 MPG, while SUVs and trucks typically range from 20-30 MPG.

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sel make | Make | Toyota=1, Honda=2, Ford=3, Chevrolet=4, Nissan=5
list model | Model (choose one) | Corolla=1, Civic=2, F-150=3, Silverado=4, Altima=5
in year | Year | 2021 | 1990
out mpg | Combined MPG | mpg | 30 | 1
out cost | Annual fuel cost | USD | (12000 / mpg) * 3.50 | 0
out co2 | CO2 (g/mile) | g/mile | 8887 / mpg | 0