Thread (yarn)

Yarns are measured by the density of the yarn, which is described by various units of textile measurement relating to a standardized length per weight. These units do not directly correspond to thread diameter.

The most common weight system for thread specifies the length of the thread in kilometres required to weigh 1 kilogram. Therefore, a greater weight number (indicated in the American standard by the abbreviation wt) indicates a thinner, finer thread. The American standard of 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, though this is not a formal requirement in the US standard (which is therefore less informative).

A denier weight specification states how many grams 9,000 metres of the thread weighs. Unlike the common thread weight system, the greater the denier number, the thicker the thread. The denier weight system, like the common weight system, also specifies the number of strands of the specified weight which were wrapped together to make the finished thread. Only embroidery threads have their weights given in denier.

Tex is the mass in grams of 1,000 metres of thread. If 1,000 m weighs 25 g, it is a tex 25. Larger tex numbers are heavier threads. Tex is used throughout North America and Europe.

Manufacturers producing fine silk threads, apply their own scales of thread measurement using "aughts" or zeroes at the finest end and FFF at the other, thus scaling 000, 00, 0, A, B, C, D, E, F, FF, FFF. The three finest threads are described as having "three aughts", "two aughts", and "one aught" respectively, and as having different "aught counts". Within a given manufacturer's spectrum, a higher "aught count" indicates a finer thread: this may be given as a single digit followed by a forward slash and a zero— for example, 3/0 indicates a three-aught thread or a thread size "000", but this number only has significance when compared to other threads produced by the same manufacturer: one manufacturer's 3/0 will always be more fine than that same manufacturer's 2/0, but may not be comparable to the 3/0 of another manufacturer. Very roughly, however, size A is 900 yards per pound of thread, and every 100 yards difference is one letter size different. The size is always given for the overall thread, not its individual silk plies.

Some heavier duty threads are given "commercial" size designations in set sizes of 30, 46, 69, 92, 138, 207, 277, 346, 415 and 554 only. Each of these numbers is merely the thread's denier size divided by 10. A commercial size 138 thread has a denier of 1380.

Thread weight conversion table

For example: 40 weight = 225 denier = tex 25 = [theoretical] commercial 27.8 . A common tex number for general sewing thread is tex 25 or tex 30. A slightly heavier silk buttonhole thread suitable for bartacking, small leather items, and decorative seams might be tex 40. A strong, durable upholstery thread, tex 75. A heavy-duty topstitching thread for coats, bags, and shoes, tex 100. A very strong topstitching thread suitable for luggage and tarpaulins, tex 265–tex 290. But a fine serging thread is only tex 13. And blindstitching and felling machines, an even finer tex 8.

Threads of different composition and construction may be labeled in a variety of ways. Most threads are composed of 2 or more "plies" of fiber, and this information is often provided on thread packaging along with the finalized thread's weight, according to a particular scale of measurement. The actual physical diameter of a thread is not recorded and is unhelpful.

Spools may have codes that indicate their fiber content as well such a "P" for polyester. If a fiber content is given in the label code, it will be the first piece if information located there.

Sometimes a manufacturer does not provide any weight specification at all on its spools and instead provides only the fiber content and spool length such as "100% Silk 250 m". This means only that the spool has 250 meters of pure silk, but does not indicate how many plies make up that thread nor what the plies' or the combined thread's weight is.

The cotton count system is based on the number of 840 yard hanks that will result from a single pound of a particular finished thread. This is the non-metric equivalent of the Gunze count, and is given with two numbers separated by a slash: the first is the size of the thread and the second is the number of plies of that size used in the finished thread. The cotton count was developed for the cotton industry, but cotton counts are also frequently given for polyester and polyester/ cotton blends as well.

A Hong Kong ticket number, when present, is a cotton count number without the slash and with the final number always indicating the number of plies if more than one. A Hong Kong ticket number of 1002 is made of two plies of size 100 thread; a number of 100 is made of a single ply of size 100 thread; a size 503 is made of three plies of size 50 thread.

A spool of thread may be described in terms of its "single's equivalent". This is the cotton count size of the thread divided by the number of plies which make it up. A spool of 30/3 thread has a single's equivalent of 10, because a single strand or ply of that thread has a cotton count size of 10. A 20/2 spool has the same single's equivalent as a 30/3, but a 30/2 spool has a single's equivalent of 15, which means it is composed of individually heavier plies than a 30/3.