Units of measure for fibers

The linear density of a fiber is commonly measured in units of denier or tex. Traditional units include worsted count, cotton count and yield. 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 International System of Units uses kilogram per metre for linear densities; in some contexts, the tex unit is used instead.

Denier

Denier or den (abbreviated D), a unit of measure for the linear mass density of fibers, is defined as the mass in grams per 9000 meters. The denier is based on a natural reference: a single strand of silk is approximately one denier; a 9000-meter strand of silk weighs about one gram.

One can distinguish between filament and total measurements in deniers. Both are defined as above, but the first relates to a single filament of fiber — commonly known as denier per filament (DPF) — whereas the second relates to a yarn.

Broader terms such as 'fine' may be applied, either because the overall yarn is fine or because fibers within this yarn are thin. A 75-denier yarn would be considered fine even if it contains only a few fibers, such as thirty 2.5-denier fibers, but a heavier yarn, such as 150 denier, is only considered fine if its constituent fibers are individually as thin as one denier.

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 denier= 1 gram per 9000 meters

= 0.11 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 is multiplied by ten to obtain the denier weight.

• A fiber is generally considered a microfiber if it is one denier or less.

• A one-denier polyester fiber has a diameter of about ten micrometers.

• In tights and pantyhose, the linear density of yarn used in the manufacturing process determines the opacity of the article in the following categories of commerce: ultra sheer (below 10 denier), sheer (10 to 30 denier), semi-opaque (30 to 40 denier), opaque (40 to 70 denier) and thick opaque (70 denier or higher).

For single fibers, instead of weighing, a machine called a vibroscope is used. A known length of the fiber (usually 20mm) is set to vibrate, and its fundamental frequency measured, allowing the calculation of the mass and thus the titer.

Tex

Tex is a unit of measure for the linear mass density of fibers, yarns and thread and is defined as the mass in grams per 1000 meters.[4] 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.

Yield

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.

GSM of fabric

In the International System of Units, surface density is measured in kilograms per square meter. For fabrics, grams per square meter (GSM) is a more practical unit of measure.

Mommes

Mommes (mm), traditionally used to measure silk fabrics, the weight in pounds of a piece of fabric if it were sized 45 inches by 100 yards. One momme = 4.340 grams per square meter; 8 mommes is approximately 1 ounce per square yard or 35 grams per square meter.

Thread count or threads per inch

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.

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.

Picks per inch

Picks per inch/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.