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.

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**.

The metre, or meter (American spelling), is the base unit of length in the International System of Units (SI). The SI unit symbol is m. The metre is defined as the distance travelled by light in a specific fraction (1/299 792 458) of a second. The imperial inch is defined as 0.0254 metres (2.54 centimetres or 25.4 millimetres). One metre is about 3 3⁄8 inches longer than a yard, i.e. about 39 3⁄8 inches.

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.

Measurements most commonly use the *International System of Units* (SI)
as a comparison framework. The system defines seven fundamental units:
kilogram, metre, candela, second, ampere, kelvin, and mole.