Carbon Footprint Calculator Formula

Understand the math behind the carbon footprint calculator. Each variable explained with a worked example.

Use the Carbon Footprint Calculator

Formulas Used

Total Annual CO2

total_co2_lbs = driving_co2 + electric_co2 + gas_co2 + flight_co2

In Metric Tons

total_co2_tons = (driving_co2 + electric_co2 + gas_co2 + flight_co2) / 2204.6

Driving CO2

driving_share = driving_co2

Home Energy CO2

home_share = electric_co2 + gas_co2

Variables

VariableDescriptionDefault
miles_drivenAnnual Miles Driven(miles)12000
vehicle_mpgVehicle MPG(MPG)28
electricity_kwhMonthly Home Electricity(kWh)900
gas_thermsMonthly Natural Gas(therms)40
flight_hoursAnnual Flight Hours(hrs)10
driving_co2Derived value= miles_driven / vehicle_mpg * 19.6calculated
electric_co2Derived value= electricity_kwh * 12 * 0.92calculated
gas_co2Derived value= gas_therms * 12 * 11.7calculated
flight_co2Derived value= flight_hours * 90 * 2.2calculated

How It Works

How Carbon Footprint Is Estimated

Your carbon footprint includes emissions from transportation, home energy, and air travel.

Emission Factors Used

  • Driving: 19.6 lbs CO2 per gallon of gasoline
  • Electricity: 0.92 lbs CO2 per kWh (US average)
  • Natural Gas: 11.7 lbs CO2 per therm
  • Flights: ~90 kg CO2 per flight hour per passenger (x 2.2 for lbs)

    • Worked Example

    12,000 miles at 28 MPG, 900 kWh/mo electricity, 40 therms/mo gas, 10 flight hours.

    miles_driven = 12000vehicle_mpg = 28electricity_kwh = 900gas_therms = 40flight_hours = 10
    1. 01Driving = 12,000 / 28 x 19.6 = 8,400 lbs CO2
    2. 02Electricity = 900 x 12 x 0.92 = 9,936 lbs CO2
    3. 03Natural gas = 40 x 12 x 11.7 = 5,616 lbs CO2
    4. 04Flights = 10 x 90 x 2.2 = 1,980 lbs CO2
    5. 05Total = 8,400 + 9,936 + 5,616 + 1,980 = 25,932 lbs = 11.8 tonnes

    Frequently Asked Questions

    What is the average carbon footprint in the US?

    The average American produces about 16 metric tonnes of CO2 per year, one of the highest per-capita rates in the world. The global average is about 4 tonnes.

    How can I reduce my carbon footprint?

    Drive less or switch to an EV, improve home insulation, use renewable energy, fly less, eat less meat, and reduce waste.

    What is a carbon offset?

    Carbon offsets fund projects that reduce emissions elsewhere (tree planting, renewable energy, methane capture) to compensate for your own emissions.

    Ready to run the numbers?

    Open Carbon Footprint Calculator