How do we work it all out?

This page endeavours to demonstrate the depth and accuracy of our methodology without boring the pants off of you. This is a strictly interested-enough-for-pants zone. Do read on.

Carbon numbers

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    Our carbon data is supplied by Professor Mike Berners-Lee’s Small World Consulting, experts in the field of carbon measurement and assessment.
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    Our calculator uses a top-down model when it comes to measuring a user’s personal Pawprint. This means we take the total emissions of a country, allocated by industries, and break it down for the average resident. In the UK, for example, this gives us a figure of 13.1 tonnes CO₂e per person. We then modify this starting score according to survey answers and ONS averages.
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    The actions in our eco-library use a bottom-up model. This means we’ve assigned a carbon number to each behaviour. As users log their actions, we add it all up to show them their estimated carbon savings.

Small World’s emissions factors are drawn either from either a top-down or a bottom-up methodology, or a blend of the two. Each has its own strengths and weaknesses, so combining them gives us the best of both worlds.

Ultimately, we rely on the information you give us to ensure you receive the most accurate figures possible, meaning our survey answers are as important as our methods!

Dive deeper

Want to really get into the weeds of our methodology? Download our full methodology document below.
Download PDF

Cost savings

To highlight the fact that sustainable choices often have a financial benefit, we’ve attached estimated cost savings to many of our actions. How do we get these estimates, you ask? It’s quite simple—our carbon calculations are based on the energy usage of that action. We then take those numbers, and figure out the monetary cost of that energy.

For example, when we’re calculating the cost savings of, say, cycling or walking instead of driving, we look at the cost of petrol per litre, then multiply that by the miles driven and the vehicle’s fuel efficiency.

Our cost calculations are based on current market rates in the UK and Europe, but that isn’t to say we’re aiming for perfect accuracy! There are plenty of other factors that can influence the cost savings of an action—for instance, some figures are harder to estimate since they use demand-based pricing, like flights and taxis.

This is why each of our calculations comes with a range of savings, rather than a single figure. It allows users to use their own judgement to decide where their personal saving will lie.

Dive deeper

Curious about how we crunch these cost savings? Download our formulas sheet below.
Download our cost savings data

Ready to take the next step?

Talk to our team