Carbon Calculator Reviews for Consumers: Round 2

As promised, here is the second round of carbon calculators reviews for tools meant for everyday consumers.  You can see our previous reviews in PART 1.

Carbon versus Carbon Dioxide

But first, a note on defining carbon versus carbon dioxide (CO2). Many (most) of the calculators on this list compute one’s impact in terms of the quantity of CO2 emitted, in tons.

It is important to know that these two words cannot be used interchangeably. CO2 is the gas emitted by burning fossil fuels and other industrial processes. When referenced as it relates to emissions, “carbon” is being referred to as the quantity of carbon in carbon dioxide, calculated using the ratio of carbon and oxygen’s atomic weights to one another. A simple math equation, but a math equation for another day.

Types of Greenhouse Gases

It is also important to know there are other greenhouse gasses than just CO2. Shocking! Methane (CH4), nitrous oxide (N2O), and carbon dioxide are the main three, but not the only three (see image at left). 

To get around the confusion of reporting quantities of different greenhouse gasses, carbon calculators (and many actors 

in this space) convert all the different greenhouse gasses into an equivalent impact from carbon dioxide, the most common gHg emitted by humans. This is why this symbol, CO2e or CO2eq, may look familiar to you. This might also be why the name of this series should be changed from carbon calculators to carbon dioxide calculators.

Carbon Calculator Review Continued

First up: the UN’s Carbon Footprint Calculator.

This calculator is fairly basic. There is not much to say about this calculator and that, in itself, says something. The calculator lives on the organization’s carbon offset platform which certifies projects in developing countries that intend to reduce GhG emissions. The platform asks individuals to buy Certified Emission Reductions (CERs) in support of many projects.

It feels like the calculator is designed not for the inherent purpose of quantifying individuals’ emissions. Rather, it feels made for the larger purpose of reframing their bid for donations to a more noble pursuit of helping individuals offset their own emissions.

The calculator itself is divided into the three classic categories: household, transport, and lifestyle. What I do not love about this calculator is a trifecta of things:

  1. The questions feel shallow and non-exhaustive.
  2.  There is no additional information on the calculator’s methodology and data easily accessible. So the user has no sense of how current the data is. 
  3. Further, this calculator makes the process of calculating one’s emissions fairly cumbersome.

To elaborate, most calculators ask questions to estimate the user’s emissions data. In comparison, the UN’s calculator asks for raw data in a few different spots (size of their housing in m2, energy usage). For the sake of comparison take this example: a calculator might ask how often the individual turns off the lights when they leave a room. Instead, the UN calculator asks an individual for their home electricity consumption in KwH outright. This element makes the calculator tricky for people that might not be able to access to these numbers. With that said, the calculator’s coverage of most countries in the world is impressive, if nothing else.

Next up: Conservation International.

This calculator is built for US residents and allows one to complete calculations for oneself, a household, an event, or a single trip. Once again, the calculator features the classic 3 categories: household, transportation, and travel.

The product of this calculator is your annual footprint in tons of CO2. It also tells users how many trees per year it would require to absorb all of that CO2. The organization then offers up the opportunity to offset one’s footprint by contributing to CI’s carbon offset program.

This is beginning to sound very similar to the UN calculator discussed above. On top of this, the calculators’ questions closely resemble one another. Though CI’s does this more intuitively and effectively. Instead of asking for the distance individuals travel in an average week, this calculator asks how many hours individuals spend in the car each week.

Overall, if you are a U.S. resident I would push one towards this calculator over the UN’s less-adequate version. If you live outside the U.S….well then, just keep reading.

The UN is not entirely irredeemable though. Over the years they collaborated with other organizations to create a number of carbon calculators, some of which are no longer available.

One of the calculators endorsed by the UN is none other than The 2030 Calculator.

While this calculator technically falls outside the limiting factor of  ‘calculators for consumers’, it is still included in this list. This is because it might be the most accessible of the calculators meant to target brands. Unlimited access is available at a price of €39.90/month. This platform is meant to be used by any brand  to calculate the carbon footprint of one’s products. This includes all emissions from manufacturing, transport, and up until the point of sale. The site does this by identifying the emissions factors for each individual product part and the associated processes. (packaging, transport, manufacturing). ‘Cradle-to-gate’ is what this type of coverages is often referred to.

The SHIFT team is working to answer the question “How do we quantify/calculate the impact (avoided emissions) from the SHIFT program?”. This tool radically simplifies carbon calculations for a great deal of products. Of course, the tool’s usefulness depends on if the materials relevant to one’s product are included in its database. With this said, the organization will provide custom impact factors upon request at no additional charge. The numbers behind this calculator come from a variety of open-data sources, primarily based in the EU.

Sweden-based Doconomy is the primary creator behind this calculator that aims to ‘democratize impact transparency’. It is their belief that carbon labeling could transform consumer decision-making and motivate brands to lessen their impact during production.

In stark contrast to this flashy new startup is a calculator by a veteran in the environmental advocacy space, given their founding in 1961. The WWF, or World Wildlife Fund, has the benefit of brand recognition among the public. This level of seniority also encourages consumer trust.

The WWF’s carbon footprint calculator is a self described questionnaire.

Do not let the informal title fool you, because the WWF doesn’t mess around. The WWF’s footprint calculator may possess the most thorough publicly-available methodology. They outline their decision-making process related to recent updates, data adjustments for inflation, and even take a critical eye towards their data sources (primarily the UK’s Office of National Statistics). Their site answers the user’s questions before they even get a chance to ask, “Not from the UK? Our results are measured against UK targets so they won’t accurately reflect your region but there’s still lots to learn about your impact.”.

One aspect of this calculator that stuck out is its emphasis on “government spend”. An excerpt from the WWF site says the following:

“To avoid the worst impacts of climate change, we need to keep global warming below 1.5°C. If everyone on the planet were allocated a ‘fair share’ of global carbon emissions, each persons footprint should be around 1 tonne by the year 2050 – as the “government spend” is already more than twice this level it is obviously not possible yet to get to this level.” (WWF 2023).

Their emphasis on this concept feels well-founded when you look at it in the way described above. This calculator gives the user their footprint in tonnes of CO2 equivalent and compare that footprint to the UK and world averages. This impact is then translated into how many tons of animal your footprint is equal to, whether that be 3 polar bears or 7 amur tigers or 18 giant pandas.

Overall our carbon calculator review for this tool is as follows: its best use is to find out how one’s impact compares to the world’s average (6.3 tonnes); in other words, it is highly effective at determining where your impact falls in relation to the larger spectrum of emissions quantities. Meanwhile, the actual number it produces quantifying one’s impact is limited by the brevity of the questionnaire. The WWF’s methodology and commitment to sharing it should act as an example to all other calculators as the industry-expectation.


The intention of each of these tools is not to take the place of a complete life cycle analysis, but rather provide an approximation that offers one a starting point for looking into their carbon emissions. One must always keep this in mind when utilizing these tools. It is always a balance between accessibility and precision and each individual must decide what that balance looks like for themselves.

This carbon calculator review is a series of three posts in which we break down and review the different carbon calculators available freely to consumers.