Denier
Also searched as: den, D, linear density
A linear density unit: grams per 9,000 meters of yarn or fiber.
In detail
Denier measures mass per length: a 9,000-meter length with a mass of 1 gram is 1 denier. A larger number means more mass for the same length. The unit may describe an individual filament or a whole yarn, so the object being measured must accompany the number.
The science and numbers
Because denier is mass per 9,000 meters, conversion to the other linear-density units is a fixed ratio: tex (grams per 1,000 m) equals denier divided by 9, and decitex (grams per 10,000 m) equals denier divided by 0.9, so 1 denier is about 1.11 dtex. For diameter, the polymer density is also needed: for a solid round filament, mass per length equals density times cross-sectional area, so in cgs units d (cm) = sqrt(4 x denier / (pi x density x 900,000)), since 9,000 m is 900,000 cm. With d in micrometers and density in g/cm3 this becomes denier = 0.00707 x d squared x density, or d = 11.89 x sqrt(denier / density). A 15 micrometer polypropylene filament (density about 0.89 g/cm3) therefore works out to roughly 1.4 denier. Hollow or non-round sections need the measured cross-sectional area instead.
A practical example
A 90-denier yarn has a linear density of 10 tex because tex uses grams per 1,000 meters. If that yarn contains 30 equal filaments, each is nominally 3 denier. These are calculated examples, not measurements of a particular fabric.
What to distinguish
Denier is not a direct diameter, thread count or fabric-weight measurement. Material density, cross-sectional shape, filament count and fabric construction prevent a simple universal conversion from denier to softness, opacity or durability.
Origins and history
The unit borrows the name of a coin. English denier comes through French from Latin denarius, a Roman coin whose name derives from deni, 'ten each'. A Frankish silver denier was first issued in the late seventh century, and in France the denier survived as one twelfth of a sou until it was withdrawn in the 19th century. Silk was traditionally weighed against this small coin, and the modern definition fixes the practice as 1 gram per 9,000 meters, a length at which a single silk strand weighs roughly one gram.
Related terms
Sources & further reading
- CottonWorks: Denier
- Online Etymology Dictionary: Denier
- Merriam-Webster: Denier definition and meaning
- ScienceDirect Topics: Filament diameter
Technical references reviewed 2026-09-22. Examples are illustrative. Industry organizations and manufacturers describe their own fields; their references are not independent product endorsements. Figures are approximate and depend on the stated test conditions.