Calculation methodology

This document provides additional detail about some of the calculations behind our sustainability messages. 

Total bottles transformed

How we calculated that more than 125 million single-use plastic bottles have been transformed into our signature thread.

As of March 2022, Rothy’s has purchased 1,188,184 kilograms of yarn, which is made from 100% post-consumer recycled plastic bottles, as certified by the SCS Recycled Content certification.

To calculate the total bottles transformed, we use a representative 16.9-ounce bottle weighing 9.25 grams, the average weight of a water bottle in 2014 according to Beverage Marketing Corp (link). There is no standard bottle weight, and the weights of plastic bottles vary across brands and markets, so we use this representative bottle weight to account for that variability. 

In the recycling process, there is some material loss due to color variations, quality and other factors. Because of this material loss, the total number of bottles collected to make 1,188,184 kilograms of yarn could be greater than 125 million bottles.

1,188,184 kilograms = 1,188,184,000 grams¸ 9.25 grams of plastic per bottle = 128,452,324 bottles

Total ocean-bound marine plastic

How we calculated that more than 400,000 pounds of ocean-bound marine plastic have been turned into the thread we use for our bags and accessories.

As of March 2022, Rothy’s has purchased 187,309 kilograms (412,945 pounds) of ocean-bound marine plastic yarn. The yarn is OceanCycle certified, verifying that the plastic was collected  from land within 30 miles proximity to the coastline.

In the recycling process, there is some material loss due to color variations, quality and other factors. Because of this material loss, the total amount of ocean-bound marine plastic collected to make 187,309 kilograms of ocean-bound marine plastic yarn could be greater than 400,000 pounds.

Total plastic bottles per shoe

How we calculate the number of plastic bottles that it took to knit each shoe type.

To calculate the number of plastic bottles that it took to knit each shoe type, we use the weight of rPET yarn used in the upper for the standard sample size of that style of women’s or men’s shoes. The women’s sample shoe is size 7, and the men’s sample shoe is size 9.

To calculate how many bottles, we use a representative 16.9-ounce bottle weighing 9.25 grams, the average weight of a water bottle in 2014 according to Beverage Marketing Corp (link). There is no standard bottle weight, and the weights of plastic bottles vary across brands and markets, so we use this representative bottle weight to account for that variability. 

For example:

The rPET knit for the upper of The Point in women’s size 7 weighs 106.3 grams.

106.3 grams of rPET knit in the upper / 9.25 grams of plastic per bottle = 11.4 bottles.