Textile yarns are measured in various units, such as: the denier and tex (linear mass density of fibres), super S (fineness of wool fiber), worsted count, woolen count, cotton count (or Number English Ne), Number metric (Nm) and yield (the inverse of denier and tex). Yarn is spun thread used for knitting, weaving, or sewing. Thread is a long, thin strand of cotton, nylon, or other fibers used in sewing or weaving. Both yarn and thread are measured in terms of cotton count and yarn density.
Denier or den is a unit of measure for the linear mass density of fibers. It is defined as the mass in grams per 9000 meters. The denier is based on a natural reference—i.e., a single strand of silk is approximately one denier. A 9000-meter strand of silk weighs about one gram. The term denier comes from the French denier, a coin of small value (worth 1⁄12 of a sou). Applied to yarn, a denier was held to be equal in weight to 1⁄24 of an ounce. The term microdenier is used to describe filaments that weigh less than one gram per 9000 meters.
The International System of Units uses the unit kilogram per metre for linear densities; in some contexts the unit "tex" is used instead.
The following relationship applies to straight, uniform filaments:
DPF = total denier / quantity of uniform filaments
The denier system of measurement is used on two- and single-filament fibers. Some common calculations are as follows:
= 1 gram per 9 000 meters
= 0.111 milligrams per meter
In practice, measuring 9000 meters is both time-consuming and unrealistic; generally a sample of 900 meters is weighed and the result multiplied by 10 to obtain the denier weight.
Tex is a unit of measure for the linear mass density of fibers and is defined as the mass in grams per 1000 meters. Tex is more likely to be used in Canada and Continental Europe, while denier remains more common in the United States and United Kingdom. The unit code is "tex". The most commonly used unit is actually the decitex, abbreviated dtex, which is the mass in grams per 10,000 meters. When measuring objects that consist of multiple fibers the term "filament tex" is sometimes used, referring to the mass in grams per 1000 meters of a single filament.
Tex is used for measuring fiber size in many products, including cigarette filters, optical cable, yarn, and fabric.
S or super S number
S or super S number is an indirect measure of the fineness of the wool fiber. It is most commonly seen as a label on wool suits and other tailored wool apparel to indicate the fineness of the wool fiber used in the making of the apparel. The numbers may also be found on wool fabric and yarn.
Worsted count (or spinning count) is an indirect measure of the fineness of the fiber in a worsted wool yarn expressed as the number of 560-yard  (1 yard = 0.9144 meters) lengths (hanks) of worsted yarn that a pound (0.45359237 kilograms) of wool yields. The finer the wool, the more yarn and the higher the count. It has been largely replaced by direct measures.
Similar to tex and denier, yield is a term that helps describe the linear density of a roving of fibers. However, unlike tex and denier, yield is the inverse of linear density and is usually expressed in yards/lb.
· Cotton count is another measure of linear density. It is the number of hanks (840 yd or 770 m) of skein material that weigh 1 pound (0.45 kg). Under this system, the higher the number, the finer the yarn. In the United States cotton counts between 1 and 20 are referred to as coarse counts. A regular single-knit T-shirt can be between 20 and 40 count; fine bed sheets are usually in the range of 40 to 80 count. The number is now widely used in the staple fiber industry.
· Hank: a length of 7 leas or 840 yards (770 m)
One lea – 120 yards (110 m)
Thread count or threads per inch (TPI) is a measure of the coarseness or fineness of fabric. It is measured by counting the number of threads contained in one square inch of fabric or one square centimeter, including both the length (warp) and width (weft) threads. The thread count is the number of threads counted along two sides (up and across) of the square inch, added together. It is used especially in regard to cotton linens such as bed sheets, and has been known to be used in the classification of towels.
Thread count is often used as a measure of fabric quality, so that "standard" cotton thread counts are around 150 while good-quality sheets start at 180 and a count of 200 or higher is considered percale.
Ends per inch
Ends per inch (EPI or e.p.i.) is the number of warp threads per inch of woven fabric.In general, the higher the ends per inch, the finer the fabric is. The current fashion is to wear t-shirts with a higher thread count, such as soft and comfortable "30 single" tee shirt that has 30 threads per inch as contrasted to the standard t-shirt with an 18 thread count per inch.
Ends per inch is very commonly used by weavers who must use the number of ends per inch in order to pick the right reed to weave with. The number of ends per inch varies on the pattern to be woven and the thickness of the thread. Plain weaves generally use half the number of wraps per inch for the number of ends per inch, whereas denser weaves like a twill weave will use a higher ratio like two thirds of the number of wraps per inch. Finer threads require more threads per inch than thick ones, and thus result in a higher number of ends per inch.
The number of ends per inch in a piece of woven cloth varies depending on what stage the cloth is at. Before the cloth is woven the warp has a certain number of ends per inch, which is directly related to what size reed is being used. After weaving the number of ends per inch will increase, and it will increase again after being washed. This increase in the number of ends per inch (and picks per inch) and shrinkage in the size of the fabric is known as the take-up. The take-up is dependent on many factors, including the material and how tightly the cloth is woven. Tightly woven fabric shrinks more (and thus the number of ends per inch increases more) than loosely woven fabric, as do more elastic yarns and fibers.
v Picks per inch (or p.p.i.) is the number of weft threads per inch of woven fabric. A pick is a single weft thread,hence the term. In general, the higher the picks per inch, the finer the fabric is.