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How we calculate our impact (2024 update)

Bobbie, February 2, 2024

Every item borrowed has a positive impact on people and the planet which we quantify with our impact calculation methodology. In line with our commitment to transparency, below we share this methodology, including how and why measures and assumptions have changed.

The methodology builds on Library of Things’ original impact calculator that was designed with inputs from consultants Naomi Jones and M2, who were commissioned by Nesta to do an independent evaluation of Library of Things’ impact.

Like all similar calculators, we know it is an imperfect way of calculating our impact and has its limitations which is why we periodically review and update our formulae and reporting to improve its accuracy.

How has the impact calculation changed?

⬆️ % of borrows that prevent a purchase - increased from 25% to 50% based on the findings of our most recent Impact Survey ⬇️ % of users more likely to repair or recycle items having borrowed - reduced from 60% to 50% based on the findings of our most recent Impact Survey ⬆️ Average RRP of LoT item, if purchased new - increased from £140 to £297 based on the weighted average RRP of Things borrowed in 2023 ⬆️ Average borrow value - increased from £11 to £11.38 based on the average value per borrow in 2023 🆕 Electricals re-used - the weight of electricals re-used based on an average Thing weight of 7kg

Impact measures

💰 Money saved by borrowers through purchase avoidance

Affordable access to borrowing means that rather than someone needing to buy a new Thing for hundreds of pounds, they can borrow it for a few pounds a day instead. With many things only needed for a specific project or a few times a year, the savings for one household quickly become very significant.


  • 50% of borrows prevents a purchase
  • The difference between the average cost of a borrow and the average cost to buy = £286
  • Each borrow saves on average £286 x 50% = £143

Limitations & future development: We acknowledge this does not account for: variations in product purchase price (for example through discounts or second-hand sales), variations in the product model and brand that a user might have chosen if they were to purchase the product, or the purchase price of all of the products within Library of Things’ catalogue.

👣 Extra visits to community spaces

Borrowing prevents waste directly through fewer items being bought (and therefore one day ending up in the bin) and indirectly through behaviour as people who borrow embrace other circular behaviours such as recycling and repair.


Direct: Waste prevented through borrowing

  • 50% of borrows prevents a purchase
  • The average weight of a Thing is 7kg
  • Each borrow therefore prevents 3.5kg of waste on average

Indirect: Waste prevented through behaviour change

  • 50% borrowers more likely to repair/recycle items
  • Each of these people on average has 2 additional items repaired/recycled
  • Each item has a weight of 5.5kg avg weight of item repaired/recycled
  • Each borrower therefore prevents 5.5kg (50% x 2 items x 5.5kg) of waste on average

Limitations & future development: We acknowledge this calculation is underpinned by multiple assumptions some of which are based on anecdotal evidence collected at a point in time. Specifically, the number of additional items we estimate our users to reuse, repair or recycle per year as a result of engaging with LoT (two), and the average weight of each of these items (5.5kg). The other nuance not accounted for under direct waste prevention is the lag time between a new purchase and eventual waste, as this quickly becomes very complex! This means that a part of this figure accounts for future waste prevented, as well as waste prevented within this time period.

💨 Emissions prevented

Borrowing prevents CO2 emissions (CO2e) firstly through fewer items needing to be manufactured in the first place and secondly emissions saved through less the waste being generated

Logic: Manufacture avoidance

  • 50% of borrows prevents a purchase
  • The average CO2e to manufacture a Thing is 28kg
  • Each borrow therefore prevents 24kg of CO2e on average

Waste reduction

  • 1kg of waste is equivalent to 1kg of CO2e
  • For every 1kg of waste that is prevented, 1kg CO2e is prevented

Limitations & future development: This calculation does not account for emissions and embedded carbon in the product packaging, shipping and distribution processes. The WRAP study and report about embedded carbon is from 2009-10 (though we haven’t been able to find robust studies specific to the type of products in LoT’s catalogue). We acknowledge that preventing a purchase does not immediately directly prevent a decision to manufacture a product – there is a lag time between demand reduction and supply reduction. Finally we acknowledge our catalogue contains a diverse range of products with different raw materials and manufacturing processes – from carpet cleaners to sound systems to tents – and the power drill is only a proxy for them, rather than an average.

🔌 Electricals reused

Borrowing is central to a more circular economy - each borrow enables each Thing to be used by many people time and time again. The combined weight of items borrowed in a period gives us a measure of circularity


  • The average weight of a Thing borrowed is 7kg
  • Each time a Thing is borrowed, that’s 7kg of electricals that is being reused

Limitations & future development: The calculation uses an average weight taken at a point in time and the actual weight in any given period may vary up and down from this depending on the mix of items available in our catalogue and borrowed. There are also a small number of non-electrical items in our catalogue (e.g. Tents and Gazebos) and while these make up <1% of total borrows, they are not technically electricals being reused.

We're continuing to make these complex calculations more accurate, but we felt it was important to be transparent about how we have come to our impact figures. One thing we can be sure of is that borrowing IS better than buying and having a positive impact on both people and the planet. You can read our full impact report for 2022/23 here.