About Our Calculator

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Overall Strategy

We believe in big things.

Big decisions.  Big reductions.  Big responsibility.  We also believe strongly in individual action.

It’s the one thing we can do to fight climate change that doesn’t rely on anyone else.

Our goal is to provide a concise, useable carbon footprint calculator that will identify which lifestyle choices have the biggest impact, so we can make pragmatic and informed choices on how we can make a difference.  You can learn more about the assumptions we make and how we calculate your footprint below.

The goal is also to allow anyone to test the potential impact of a major decision quickly.  For example, how much could you save by skipping that long flight?   What if you drastically changed your family’s diet and consumption habits?

We are primarily focused on reductions and eliminations that make a difference.   Our calculator isn’t a good solution for testing small marginal gains such as more efficient appliances, etc.  But our blog will address some of those points over time.

How We Calculate

Car Miles

We use 25 MPG and 19.56 pounds of CO2 emitted per gallon. This is the average all-use mileage of new cars purchased in the last few years.  The true national average of vehicles on the road is lower, but this is a nice conservative number.  If you have an incredibly efficient car or hybrid, you can adjust the miles travelled.  *more options coming soon.



Flight Miles

The calculator uses 250kg of CO2 per person per hour and assumes an average speed of 500 MPH.  These numbers are relatively conservative, but do make a reasonable adjustment for the radiative effect.  A long flight will be slightly more efficient and a short commuter flight will be less efficient.



We use 0.005 metric tons of CO2 per therm of natural gas



We use .527 kg of C02 per kWh, which is lower than the epa’s estimated average across the US of .7 kg.  This is an average and doesn’t account for your specific geography.



We use a standard per-day CO2 for 6 diet types.  We aggregated a few research papers to get us in the ballpark.  One is UK-based, but has a good methodology, the other is both the CEDA and EIO-LCA data.  Links are below




Diet is complicated.   For example, we know that things like community supported agriculture and eating closer to home can help lower our footprint, but we also know that eating organic items that aren’t found locally can actually enlarge our footprint.  Two great books are recommended as well below.  What’s clear is that the calculator will help to evaluate your “macro” diet choices concerning your level of meat consumption.




Christopher M. Jones and Daniel M. Kammen at UC Berkley have done a great job of trying to quantify the carbon footprint of households by aggregating existing research, particularly the Economic Input-Output Life Cycle Assessment model (10), EIO-LCA, designed by the Green Design Institute at Carnegie Mellon University, and the Comprehensive Environmental Database Archive (), CEDA4.0 .  We’ve taken their findings on goods and services and used it to produce a “Consumption Index” which is then converted to the appropriate yearly CO2 per person.  A value of 7 on our index equates to the average American’s impact from consumption.


HouseHold Size

For each person in your household, we apply a basic first-world infrastructure impact of 1.6 tons CO2.  This accounts for our share of things like basic social services, health care infrastructure, etc.  Basically our base impact for the privilege of living in a first-world country.  This number is very conservative.



To calculate how many “Earths” it would take to support your family’s lifestyle, we divide your total tons ofCO2 by househould size and convert it to hectares.  This tells us approximately how many hectares of land it takes to support the footprint of each member of your family.  We divide this by 1.72, the current carrying capacity of the Earth in hectares.  Essentially, this tells you how many “Earths” it would take if every person on the planet lived like you.



Contact Us

We’d love to hear from you.  jake@permanentplanet.com