Calculating Your Carbon Footprint

Reader Contribution by Aly Van Dyke

We filled out this worksheet in my environmental studies class today, and I thought I’d share with everyone. It’s a way to roughly calculate your carbon footprint and think about things you can do to reduce your personal emissions.

If nothing else, I think it’s great that schools are encouraging students to at least think about areas in our lives that contribute to carbon emissions and ways we can adopt more sustainable, conservative practices to mitigate some of the effects of these emissions.

The Facts

  • Sixty percent of man-made contributions to global warming comes from carbon dioxide emissions; 75 percent of which comes from burning fossil fuels.
  • Worldwide, each person emits an average of 1 ton carbon dioxide each year.
  • The average American emits 20 tons each year.

The Calculations

Note: If math isn’t your thing, try the online carbon calculators provided by the following organizations: EPA, Climate Crisis and SafeClimate.

Car emissions

Estimate the average miles you drive each year and your car’s average miles per gallon. The worksheet says to use 20 mpg if you’re not sure, but dividing the number of miles shown on your gage when it’s about empty by the total number of gallons in your fuel tank should get your pretty close. (For example, I know I need to fill up my Ford Focus when I get around 280 miles for my 12 gallon tank, so my car’s mpg is about 23).

Here’s the formula:

Average miles/year                   x          Average mpg                =          Gallons/year

Burning one gallon of gas emits 9 kg of carbon dioxide into the atmosphere. So to calculate your driving emissions:

Gallons/year                 x          9 kg/gallon        =          Kilograms of Carbon dioxide/year


Estimate the amount of kilowatt hours you consume each year. You can do this by either looking at your most recent electric bill and multiplying the amount of kilowatt hours you were charged for by 12, or go with the typical amount of 3,000 kWh per year.

One kilowatt hour of electricity produced from a coal-fired plant is equivalent to 1 kg of carbon dioxide emitted into the air. So your average kilowatt hours of electricity per year is equal to the kilograms of carbon dioxide emitted for its production.

See our Electricity Quiz to find out more about electricity consumption and emissions.


Estimate the average amount of energy you use each year to heat your homes (also known as British thermal units, or BTUs). The worksheet gave 60 million BTU/year as the typical amount if you don’t know yours. However, just as calculating the electricity emissions, find your last heating bill and multiply the units by 12 to get your yearly consumption.

100,000 BTUs is equivalent to 5.5 kg of carbon dioxide. Here’s the formula:

BTU/year         ÷     100,000 BTU   x   5.5 kg =    Average natural gas emissions/year

Airplane travel emissions

Estimate the number of miles you traveled by airplane last year. On average, one mile traveled by plane equals 0.23 kg of carbon dioxide emissions, so:

Number of miles of airplane travel            x       0.23 kg     =     Airplane travel emissions

For more information about travel emissions, see Tips for Eco-Friendly Travel.


Add the carbon dioxide totals highlighted in bold.

Car emissions     +      Electricity emissions       +       Natural gas emissions   + Airplane travel emissions

Food emissions

Multiple the carbon dioxide totals calculated about by 2. The worksheet said the carbon dioxide we emit indirectly through purchasing food and other goods and services is twice the amount we emit in the ways calculated above.

Total from above          x          2          =          Total carbon dioxide emissions: kg/year


Convert kilogram/year to metric ton/year:

Total carbon dioxide emissions   ÷    1,000 metric tons/year        =  Metric tons/year of carbon dioxide emissions

Then the worksheet tells us to compare this number with the average per capita carbon dioxide emissions globally and nationally.

Is your total carbon dioxide emission greater than 1 ton/year? Is it greater or less than 20 tons/year? Where do most of your emissions come from? How could you lower this amount?

I’d never calculated my emissions total before, but now knowing mine as it currently stands (a number the author cares not to share out of embarrassment) has really made me see where I need to make improvements and how much carbon dioxide I alone contribute to the global total.

Before calculating my carbon footprint, I think I applied the term “emissions” nationally, presuming my carbon feet couldn’t possibly have as large a print on the nation’s total. But with my number being so … unsatisfactory … it puts the term, and the problem, into a perspective I can relate to.