This calculator uses shop department's average weight per item, an estimate of the CO2 created per kg during manufacture, and a substitution percentage to estimate the degree to which a preloved purchase replaces a new purchase.
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Carbon footprint calculator
Calculate how much CO2 and waste you save by buying donated goods from a charity shop.

Choosing to buy second-hand rather than new helps avoid CO2 emissions produced in the manufacture of new goods.
Donating unwanted goods to a charity shop helps avoid waste going to landfill or incineration.