We're a popular, open-source estimate of carbon dioxide emissions.

The BlueSkyModel started as a project by MBA students to model their school's carbon footprint. Now it's free, open, and online.

In the fall of 2007, I met with a group of concerned students and staff at Wake Forest University's Babcock Graduate School of Management (Babcock). We wanted to calculate and lower our school's carbon footprint.

We researched several online calculators and wizards. However, few of the available tools were transparent or customizable. As a result, we decided to develop our own model.

With help from various contributors around the school, we developed a model that used simple calculations to deliver business-level accuracy. Of course, with a million dollars, a room full of academics, and a year or two, we could have been more accurate. However, we wanted a model that people could understand without a degree in chemistry.

To develop our model, we focused on the school's three major sources of carbon dioxide: kilowatt-hours, gallons of gas, and miles in the air. In March 2007, I published the model online as a resource for the school and the wider community. was born.

Over the years, we've all left Babcock and gone our separate ways. However, I've continued to maintain the site in my spare time. I believe the information is still relevant. I hope it is still helpful, and I hope it is still making a difference - no matter how small.

I hope BlueSkyModel helps you to measure your carbon footprint, and in the end, to live or work more sustainably. If it does, I'd love to hear how. Otherwise, please feel free to contact me with anything. Thank you!

Jack Clayton


Version 4.0 December 2014

  • Added Transmission section (and EPA estimate) to kilowatt-hour
  • Updated kilowatt-hour to 1.13 lbs CO2/kwh (an increase of 7.6% over previous 1.05 lbs CO2/kwh)
  • Fixed miscellaneous layout issues
  • Removed Version 1.0 (hosted at

Version 3.0 September 2014

  • Updated site to be responsive
  • Updated links to remove file extension
  • Updated gallon gas and air mile to show mass ratio calculations
  • Fixed molecular mass of octane (thanks Scott H)
  • Fixed small math error in air mile calculations
  • Updated gallon of gas to 18.07 lbs CO2/gal (an increase of 7% over previous 16.9 lbs CO2/gal)
  • Updated air mile to 53.29 lbs CO2/mi (a decrease of 0.5% from previous 53.55 lbs CO2/mi)
  • Deprecated Version 1.0 (hosted on

Version 2.0 April 2013

  • Fixed mass ratio error in gallon of gas calculations
  • Fixed octane rating mistake in gallon of gas calculations
  • Fixed gasoline density in gallon of gas calculations
  • Fixed mass ratio error in air mile calculations
  • Fixed jet fuel chemical formula in air mile calculations
  • Fixed jet fuel density in air mile calculations
  • Updated gallon of gas to 16.9 lbs CO2/gal (an increase of 20% over previous version's 14.1 lbs CO2/gal)
  • Updated air mile to 53.55 lbs CO2/mi (a decrease of 78% from previous version's 244.22 lbs CO2/mi)
  • Redesigned the site
  • Moved to (from

Version 1.0 March 2007 (hosted on

  • First release


Many thanks to our contributors around the world who have offered suggestions, made improvements, and pointed out mistakes over the years:

  • Amy B
  • Angie S
  • Bob H
  • Bryan H
  • Connie C
  • Concette G
  • Crissy R
  • Devin T
  • Emily B
  • Eric W
  • Greg L
  • Jim A
  • John O
  • Lisa S
  • Mason W
  • Neela R
  • Nick K
  • Paul T
  • Pepper I
  • Ricky P
  • Scott H
  • Scott S
  • Zongzhu C