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How we calculate our impact

Alexis, June 20, 2023

Every item borrowed has a positive impact on people and the planet which we quantify with our impact calculator.

IMPORTANT: Library of Things has published updated impact assumptions & methodology which can be found here

Transparency is one of our core values so below we share the rationale and assumptions behind our estimates of how much money, waste and emissions have been prevented by the service, and how many extra visits to high street hubs have been generated through borrowing rather than buying. The calculator 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, some of which we acknowledge below. We're working to make our formulae and reporting more sophisticated and accurate as we gather more data and insight.

💰 How much money borrowers have saved

To calculate money saved by users by affordably renting instead of buying, we first establish how many of our rentals directly prevent a purchase: at least one in four or 25%, according to our ongoing post-rental user survey. So we work out 25% of the total number of item rentals from Library of Things in a given period. For example, in the 12 months from 1st April 2022 to 31st March 2023, there were 10,065 rentals, of which 2,516 are estimated to have directly prevented a purchase.

We then look at the price of buying the same item brand new – averaged across our top 10 most rented items. This is currently £140. We subtract from this the average amount paid per rental: £10.50. This gives us the average amount saved per rental: £129.50.

We then multiply these two numbers: 2,516 rentals x £129.50 saved per rental = £325,822 saved by our users in 2022-2023. For simplicity in our communications, we round this up to £326,000.

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

illustration of person holding black sack of rubbish

🗑️ Waste prevented

To calculate the waste prevented from landfill, incineration or recycling by users renting instead of purchasing products, we calculate both waste directly prevented and indirect waste prevention through associated behaviour change.

Direct waste prevention

As with money saved, we take the number of rentals that users tell us have directly prevented a purchase: at least one in four, or 2,516 in 2022-2023.

We then multiply this figure by the average weight of our top 10 most rented products: 7 kilograms.

So in 2022-23, this was 2,516 rentals x 7kg = 17,612kg.

Indirect waste prevention

In our user surveys, 60% of our users say they are more likely to reuse, repair or recycle additional items, having engaged with Library of Things. Sometimes this is because they make use of LoT’s related services organised and/or promoted by us and/or our partners, such as repair and repurposing events. Sometimes this is because they've been made more aware of the issue of waste and potential alternatives by using the service.

Based on this, we make the assumption that 60% of our users reuse, repair or responsibly recycle at least two additional products per year, of an average weight of 5.5kg per product (including packaging).

So in 2022-23, this was 4,189 people x 2 items each x 5.5kg = 46,079kg.


We then add these two figures together to understand the total amount of waste prevented: 17,612kg + 46,079kg = 63,691kg = 64 tonnes.

Limitations & future development: We acknowledge this calculation is underpinned by multiple assumptions. Two of these assumptions require further research, as they are largely based on anecdotal evidence collected by our team over 8 years. Specifically, these are: 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 lagtime 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

To calculate emissions prevented by enabling rental instead of purchase, we calculate both the upstream and downstream emissions – or in other words, the emissions in the initial product manufacturing process, and then emissions that occur when a product is sent to landfill, incineration or recycling.

Manufacturing emissions

As with money and waste saved, we take the number of rentals that users tell us have directly prevented a purchase: at least one in four, or 2,516 in 2022-2023.

We then multiply this by an estimate of the emissions produced in the raw materials and manufacturing processes of a representative product in our catalogue, the power drill. The 2010 WRAP report, Environmental assessment of consumer electronic products, showed that the materials and manufacturing of the average power drill produces 24kg emissions. This is the figure we use in our calculation.

So in 2022-23, we estimate 2,516 rentals x 24kg emissions = 60,384kg = 60 tonnes emissions prevented.

Waste-based emissions

Emissions are also produced when a product sent to landfill, incineration or recycling. The 2018 UK Without Incineration report found that waste incinerators release an average of 1 tonne of emissions for every 1 tonne of waste. We use this as a proxy for landfill and recycling emissions.

To calculate the emissions prevented by preventing waste, we take our total waste prevented figure – in 2022-23, 64 tonnes x 1 tonne of emissions per tonne of waste = 64 tonnes of emissions prevented.


So in 2022-23, the total was 60 tonnes + 64 tonnes = 124 tonnes emissions 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 – there may be more up-to-date studies of embedded carbon in raw material extraction and manufacturing processes (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 lagtime 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.

👣 Extra visits to high street hubs

First some context – why does this matter? Library of Things co-locates its item rental service in community hubs in high street locations, such as public libraries, reuse/repair shops, shopping centres etc, because we know through our 8 years of practice that this increases community cohesion and local pride, and strengthens local economies.

In our 2018 impact research, 75% of 150 Library of Things users who completed a survey ‘felt more connected to their neighbours and neighbourhood because of Library of Things’.

One Kentish Town librarian told us in 2022, “Kentish Town Library of Things has been the biggest footfall driver we’ve ever had”.

We’ve learnt that more footfall, and more diverse local footfall, can mean:

  • improved viability of the hubs themselves – more activity and vibrancy, more people using co-located services, more people spending more money locally.
  • increased relationships and trust between local people.
  • improved access to goods and services.
  • more jobs, training and enterprise opportunities created.

To calculate the extra number of visits sparked by Library of Things, we account for:

  • Two visits per completed item rental (one to collect and one to return the item) – in 2022-23, this was 10,065 x 2 = 20,130 visits
  • A 25% uplift on this figure to account for additional visits – to look at Library of Things and pick up a flyer, or to join a related skills event or community gathering such as a launch party, repair party or ‘Tips & Tools’ demo – in 2022-23, this was 20,130 visits x 1.25 = 25,162 (rounded to 25,200)

Limitations & future development: This is a limited indication of the social impact Library of Things creates in communities and local economies. It does not bring to life the personal transformation and joy we hear about in user surveys – stories of learning new skills like DIY and sewing and the confidence this creates, plus the homes, gardens, streets, local projects, small businesses and neighbourhoods improved through affordable access to high quality items. We find it’s best to show this impact through quotes and case studies.

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 here.