Our Methodology

How do you measure my household's carbon "footprint"?

We ask questions about your home energy, daily transportation, air travel, waste and food choices. Using your answers, we calculate an estimate of how much greenhouse gas (GHG) was emitted by each activity over the course of a year. The sum total of these GHG emissions is your carbon "footprint". We use tonnes of carbon dioxide equivalent (tonnes CO2e) to measure GHG emissions. It includes all kinds of greenhouse gasses such as methane, nitrous oxide, chlorofluorocarbons (CFCs) — not just carbon dioxide — giving a more accurate measure of the total climate impact.

Project Neutral's climate impact calculator is designed to provide an accurate estimate using information the average person has at hand. We emphasize the activities that contribute the most to an individual's or household's carbon emissions.

Our calculator starts with easy-to-answer questions that give a rough estimate of your household's carbon emissions. From there, you can add more detail to refine your data. The more detail you add, the more accurate your results.

Do the math!

We calculate GHG emissions by multiplying activity data by emission factors:

GHG emissions = activity data x emission factor

When you drive a gas-powered car, the engine burns gasoline, a fossil fuel, to move the vehicle. For every litre of gasoline burned there is a specific amount of greenhouse gas pollution released. We calculate carbon emissions by multiplying the litres of gasoline (activity data) by the amount of CO2e released per litre (emission factor).

For driving, the equation would be:

Tonnes CO2e from driving = litres of gasoline x tonnes CO2e per litre of gasoline

Activity data: measuring consumption

Our activity data models allow us to estimate your household consumption, which we then convert into GHG emissions.

In some cases it's easy to figure out your activity data. For example, you can find the exact amount of natural gas used in your home by looking at your heating bill. But in other cases it's more complicated.

Let's go back to driving: you'd get the most accurate results by entering the actual number of litres of gasoline you use. But how many people can answer that? Most of us do have a rough idea of how long we spend driving on a typical day. When you enter your driving time in our Getting Started calculator, we convert time into an estimate of the number of litres of fuel burned using the industry-average mileage for your vehicle type. When you're ready to get a more accurate measure of your carbon "footprint", you can complete the Daily Transportation module and add more specific details from odometer readings and the exact vehicle you drive. (Stay tuned: we're fine-tuning this module now and it will be released soon!) And if you're one of those people who does track their actual fuel consumption, you'll be able to include that too!

Similarly, when you tell us the number of bedrooms, stories and age of a home, we estimate the total amount of natural gas used to heat it. When you tell us how many standard-sized servings of beef you normally eat each week, we estimate how many kilograms of beef your household consumes. We use published research from Natural Resources Canada and other agencies to develop these activity data models.

These simplified questions mean that you get a general estimate — not a highly precise measure — of your expected climate impact when you complete the Getting Started calculation, and it allows more people to understand their climate impact using our tools. Adding more data by completing all the modules (Home Energy, Daily Transportation, Travel, Food and Waste) gives more accurate results. And we'll continue to refine our activity models to improve the accuracy of your results.

Using Emissions Factors to calculate GHG pollution

Once we've estimated your consumption activity, we can use that to calculate the amount of greenhouse gasses released. We calculate carbon emissions by applying "emissions factors" to activity data. An emissions factor is the amount of greenhouse gasses released per unit of activity. For example: the amount of carbon pollution released per unit of driving (kg CO2e / km driven) or per unit of beef consumed (kg CO2e / kg beef).

Many GHG emissions factors are already known with a high degree of accuracy, such as the emissions from burning a litre of gasoline or using a kilowatt hour of electricity from Ontario's current energy grid. It's more challenging to estimate the carbon impact of an eight ounce steak because there's more variety in the ways that cows are raised. Surprisingly, it's even harder to estimate the carbon impact of a trip on public transit because the factors include the type of vehicle, the number of people on it and the distance it travelled. We use emissions factors from reliable published sources and we continue to update those factors whenever better data is available. Our methodology, including activity data model and emissions factors, is reviewed by experts on our Technical Advisory Panel.