A significant amount of water is used in the production of clothing and textiles – for example, to grow cotton and dye fabrics. When you buy a second hand item on Sellpy instead of a new one, you save the water that would otherwise have been used in the manufacturing process. Since no water is used in handling second hand items, Sellpy does not deduct any water consumption from its own operations.

To estimate the amount of water required to manufacture a new item, we first create a representative item for each product category. The water usage of this representative item is based on collected data on material and weight from over 120 000 items across more than 400 product categories, including clothing, accessories, and other textile products. These data provides us with insights about the material composition of previously sold items, such as the proportion of cotton and polyester in denim fabric. We then use the water consumption per kilogram of material and the item's weight to estimate the average water usage per representative item. Items listed as new condition and those sold by businesses do not contribute to water savings.

The replacement rate refers to the probability that purchasing a second hand item on Sellpy replaces the purchase of a newly produced item. This rate is based on responses from a customer survey conducted across several of Sellpy’s markets. In the survey, customers were asked about what item they purchased, why they chose to shop on Sellpy, and whether they would have bought a new equivalent item if it had not been available on our platform. We incorporate the replacement rate into our estimates for both total savings and savings made possible by our sellers.

Higg MSI is a tool used to estimate the environmental impact of materials in consumer items. We use data from Higg MSI to estimate the manufacturing emissions for new items. We believe this tool is the best one available, but we continuously work to improve our estimates to better reflect the complexity of reality.