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Carbon calculators- which one is right for you?

With the knowledge that all carbon calculators aren't made equal, I tested numerous online offerings and was shocked by the results

What makes a successful carbon calculator?

In their simplest form, carbon footprints reflect the quantity of GHG (greenhouse gas) emissions that can be attributed to an individual's lifestyle and consumption choices over a year. Numerous carbon calculators exist with various approaches to tracking and converting these choices into a single figure, expressed as carbon dioxide equivalent (CO2e). At their best, carbon calculators can educate and motivate individuals to reduce their footprint. However, inconsistent estimates and poor execution can lead to disengagement or scepticism. For this reason, I wanted to explore the current online calculators to see how my carbon footprint would vary between them and find out their strengths and shortcomings.

To ensure the results would be comparable, all the calculators derived estimates from at least four main sources of personal emissions: home energy, transportation, air travel and diet. In addition they were all customisable for my geographic region. However, some calculators included extra sources of emissions such as annual consumption of electronics and textile goods (details of the categories can be found in my full results which are linked below). After entering similar data into each calculator, I received a range of estimates, the lowest being 3.72 and highest 9.57 tonnes of CO2e. Curiously, all the results fell either at the lower or higher limits which appears to reflect the two separate approaches carbon calculators tend to take.

The first of which is a calculator that prioritises ease of use. Calculators such as the ones provided by WWF and Pawprint, streamline the process of receiving an estimate by providing multiple choice answers and basing their calculations on national average and demographic trends rather than asking for specific data on the users energy consumption. In addition, these calculators adjust for a nations consumption-based emissions, which accounts for the production emissions of goods that are manufactured abroad and imported. Some reports found that up to 50% of ones carbon footprint can be attributed to these exported emissions. Calculators such as these can provide a quick, generic estimate and are great for engaging users with their larger sources of emissions. However, these calculators won’t provide a precise estimate if the user's actions don’t align with the multiple choice options or if his or her behaviour varies drastically from the mean.

These 'ease of use' calculators derived the larger carbon estimates from the controlled set of data that was entered into all the calculators. These estimations unsurprisingly aligned close to the UK national average of 10.8.

The alternative approach are calculators that prioritise a fuller review of the user's emissions such as ones provided by Carbon Footprint Ltd and CO2 Web. These include a wider range of input categories that require exact figures for energy bills, miles travelled by various transportation, weekly meat consumption and how many pairs of shoes bought annually. These calculators are great if the user has the time and resources to accurately account for lifestyle and energy-intensive activities. However, estimating a carbon footprint with these calculators without a full account of these parameters could lead to a wildly inaccurate footprint . These calculators estimated my carbon footprint to be around 4 tonnes of CO2e. Whilst this may be closer to my actual carbon footprint it may also be due to my entering incomplete data which would lead to an underestimation.

Clearly, there is a need for greater standardisation in calculating carbon footprints to derive more consistent estimations. Hopefully, one will be developed that can be both detail-orientated and has user friendly-features so that the calculators are more accurate and engaging. There is some buzz around the concept of using machine learning to produce higher quality estimates based on the user's precise location and some basic parameters such as income and housing type. As it currently stands, the user should pick a calculator depending on how much information and time he or she has to ensure the best estimate. Irrespective of the calculator used or the size of emissions, the ultimate goal doesn’t change- reduce your footprint!

Engaging with your carbon footprint

There are a variety of ways to reduce a carbon footprint and listed here are the top 5 ways to reduce your footprint. The number one way to reduce your carbon footprint is to have fewer children. While it depends on your place and year of birth, a rough estimate of the carbon emissions someone in the western world emits over their lifetime is 820 tonnes CO2e. While this is understandably a controversial topic the fact is no other action is as effective in reducing your footprint on the world. However, lets hold that thought for now and move on to action everyone can take today to reduce their carbon footprint!

Unsurprisingly the distance and type of motor vehicle you drive can be a large contributor to your footprint. Driving is not only associated with GHG emissions but also a large source of local air pollutants that cause numerous health complications and are responsible for 40,000 premature deaths in the UK alone. Opting for alternative methods of transport or driving an electric vehicle is a great way to reduce your footprint and improve air quality in your area.

Frequent air travel can rack up a high carbon footprint quickly and is typically a large contributor to the footprints of higher-income individuals. Unfortunately, low-carbon air travel remains decades away and therefore the only way to reduce this factor is to fly less!

Heating and powering your home is typically the largest contributor to your carbon footprint, especially if you live in a small household. Therefore, one major way to reduce your carbon footprint is to increase the energy efficiency of your home. This can be done easily through insulating your home, upgrading your boiler or better still, switching to a renewable energy supplier.

Diet is estimated to contribute 16-31% towards a carbon footprint and unlike the other sources of emissions doesn’t tend to vary between demographics, everyone has to eat! Accordingly we can all reduce our carbon footprint by lowering the emissions produced in putting food on the table. This can be done by buying food produced locally and reducing the amount of animal products in a diet.

Step 3: Going beyond your carbon footprint

Carbon footprints can be a great tool for making people more conscious of the impacts their day to day activities have on the climate. The concept has clearly been successful with one survey reporting 53% of participants having calculated their carbon footprint. However, there are two major caveats in relying solely on carbon footprints as a tool to stop climate change.

1) Even if carbon footprints account for all the GHG you are responsible for they fail to encapsulate the numerous other negative externalities associated with our current way of life. Whilst GHGs are increasing earth’s temperature and the frequency of extreme weather events, our impact on the earth is multifaceted. This impact could better be summed up as our ecological footprint. This aims to quantify the impacts our activity has on a range of ecological systems including water, biodiversity and climate. This could track the impacts of microplastics entering our water supply from the life-cycle of our clothes or the biodiversity loss associated with deforestation as a result of growing demand for meat.

2) Irregardless of how small you whittle down your individual carbon footprint that alone won’t slow down climate change. Solely reducing ones own carbon footprint will have a negligible impact on the total global emissions; even at a generous estimation the average UK citizen contributes 0.00000000015% to global emissions. Thus, if individuals want to effect larger change beyond themselves they will need to pursue broader, systemic change.

While carbon calculators are great for communicating the carbon footprint of various activities and lifestyles, as a tool to limit climate change they must additionally provide information on reducing carbon footprints. Additionally being conscious of what is not included in a carbon footprint and the limitations of focusing on one's own footprint is critical.


Birnik, A., 2013. An evidence-based assessment of online carbon calculators. International Journal of Greenhouse Gas Control, 17, pp.280-293.

Mulrow, J., Machaj, K., Deanes, J. and Derrible, S., 2019. The state of carbon footprint calculators: An evaluation of calculator design and user interaction features. Sustainable Production and Consumption, 18, pp.33-40.

Jurić, Ž. and Ljubas, D., 2020. Comparative Assessment of Carbon Footprints of Selected Organizations: The Application of the Enhanced Bilan Carbone Model. Sustainability, 12(22), p.9618.

My carbon footprint results and features each calculator considered: https://docs.google.com/spreadsheets/d/e/2PACX-1vTotuznbEvzEqU8Ohu6AaUmYwWsqzm1Y8FYPkumhXrhCeOv4PCQYBUCLWuy3TppBe1JUAcsEAHFTLDu/pubhtml

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