Understanding Thread Weight 30w 40w 50w

Wt and Gunze count

The most common weight system specifies the length of the thread in kilometers required to weigh 1 kilogram. Therefore, a greater weightnumber (Abbreviation wt) indicates a thinner, finer thread. Thread weight was adopted from the Gunze Count standard of Japan which uses two numbers separated by a forward slash. The first number corresponds to the wt number of the thread and the second number indicates how many Strands of fiber were used to compose the finished thread. It is common to wrap three strands of the same weight to make one thread.
Thread Weight Table
Weight Gunze Count Common Use
Light 60 wt # 60/3 Bobbin or appliqué
Thin 50 wt # 50/3 Bobbin or appliqué
Regular 40 wt # 40/3 Quilting
Upholstery 30 wt # 30/3 Decorative
Heavy 20 wt # 20/3 Decorative


The numbers that trail the slash are the number of plies that make the final, Stitch-ready thread. All threads are called plies. These plies are twisted together to create the thread we use to sew and quilt.

The problem with classifying all # 50 threads as a 50 wt. thread is that a 50/2 thread and a 50/3 thread are different. The first number follows the Gunze Count standard and indicates the thread size. The larger the number, the finer the thread a 50/2 will be thinner than a 30/2. The second number indicates the number of Strands, or plies, twisted together.r. It is obvious that a 50/3 is heavier than a 50/2 because it has three Strands of a size 50 thread twisted together and the 50/2 has only two.   

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