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Denier is a unit of measure for the linear mass density of fibers. It is defined as the mass in grams per 9,000 meters.
In the International System of Units the tex is used instead (see below).
One can distinguish between Filament and Total denier. Both are defined as above but the first only relates to a single filament
of fiber (also commonly known as Denier per Filament or D.P.F) whereas the second relates to a yarn, an agglomeration of filaments.
The following relationship applies to straight, uniform filaments:
D.P.F. = 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 9 000 meters
= 0.05 grams per 450 meters (1/20 of above)
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 Europe, while denier remains more common in the United States.
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 10,000 meters of a single filament.
Tex is used for measuring fiber size in many products, including cigarette filters, optical cable, yarn, and fabric.
A fiber is generally considered a microfiber if it is 1 denier or less.
A 1-denier polyester fiber has a diameter of about 10 micrometers.
Denier is used as the measure of density of weave in tights and pantyhose, which defines their opaqueness.