Our calculation methodology.

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

Total bottles transformed

How we calculated that 225,794,969 (225 MM+) single-use plastic bottles have been transformed into our signature thread.

As of October 27, 2025, Rothy’s has purchased 2,088,603 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. 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 2,088,603 kilograms of yarn could be greater than 225,794,969 bottles.

2,088,603 kilograms =   2,088,603,000  grams / 9.25 grams of plastic per bottle = 225,794,969 bottles

Total plastic bottles per silhouette

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, men’s or kids’ shoes. The women’s sample shoe is size 7, the men’s sample shoe is size 9, and the kids’ sample shoe is kids’ size 13.

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. 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.

 

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

To calculate the number of plastic bottles that it took to knit each accessory, we use the weight of the rPET yarn used in the knit body of the accessory (ie. handbag, bag strap, etc).

Total pounds of cardboard saved

How we calculated that 3,300,00 pounds of cardboard have been saved by shipping our shoes in our sturdy boxes.

Pounds of cardboard saved (avoided usage) has been calculated by multiplying Rothy’s total single-shoe shipments since 2017 by the weight of standard small cardboard outer box (we used 0.5 lbs) that would have been used as an outer box for single-shoe shipments.

Source: Standard Box Weights

Please note: The calculations are hypothetical. Rothy’s does not ship the shoebox within another box, so the calculation of “cardboard saved” is truly cardboard avoided because we ship our products in their own box.

Equivalencies

Cardboard: 3.3+ million pounds

Asian Elephant: 300 Asian elephants

Source: WWF

Calculation: Asian elephants are the largest land mammal on the Asian continent. On average, an adult Asian elephant weighs up to 11,000 pounds. Rothy’s is assuming the weight of 11,000 pounds for each elephant.

Cardboard Surface Area

3.3+ million pounds ~ 6.6 million boxes

Small box dimensions: 12in x 9in x 6in

Formula Surface Area = 2 l w + 2 l h + 2 h w

Surface Area of each box (in ft) = 3.25ft2

Total surface area: 6.6 million x 3.25 = 21,450,000 ft2

Football Field: One football field is 57,600 ft2

The surface area of the cardboard we have avoided using (by shipping single item e-com orders in their shoe box) would cover over 370 football fields.