The Tex system (most likely derived from the word textile) was created as a new standard of consistent thread measurement and intended to replace all other methods of measurement of threads. It hasn’t quite achieved that goal because quilters love the weight standard and the number standard (for example, 40 wt. or #50) and embroiderers are used to the denier standard (120d/2). Because the International Organization for Standardization (IOS) has adopted the Tex system, it will probably continue to gain in popularity so it would be advantageous to understand it.
Tex is an accurate measurement and is considered a direct numbering system, meaning the higher the Tex number, the heavier the thread. On the other hand, the weight system, most popular in the U.S., is not a direct numbering system because the larger the number (30 wt., 40 wt., 50. wt., 60 wt.), the finer the thread. That can be confusing.
The Tex standard uses 1,000 meters of thread per gram as the starting point. This means if 1,000 meters of thread weighs one gram, it is Tex 1. If 1,000 meters of thread weighs 25 grams, it is Tex 25.
Although this appears to be a very accurate measurement, it is necessary to remember that 1,000 meters of cotton will not weigh the same as 1,000 meters of like-diameter polyester. Therefore, when comparing thread sizes based on the Tex or any other standard of measure, for exact accuracy, compare cotton to cotton, poly to poly, and silk to silk.
We use the Tex measurement on some of our newer threads and on all our industrial (apparel and upholstery) threads.
For quilting and embroidery threads, the following measurements are true:
Fine Tex Threads . . . . . . Tex 9 to Tex 20
Medium Tex Threads . . . Tex 21 to Tex 70
Heavy Tex Threads . . . . . Tex 71 and higher
Please click on the diagram below to view full size.