Hong Life CalculatorsUnderstanding the denier and tex converter — concept and principle
This converter translates the linear density of fibres and yarns between denier, tex and decitex (dtex). These numbers describe how heavy a given length of thread is, which is the textile industry's practical way of saying how thick it is. You meet them on outdoor fabric labels (70D nylon), stockings, sewing thread and filament specifications.
How it is calculated
All three units are "direct" systems: mass in grams per fixed length.
- denier (D) = grams per 9,000 m
- tex = grams per 1,000 m
- decitex (dtex) = grams per 10,000 m
Because only the reference length changes, the factors are exact: 1 tex = 9 denier = 10 dtex, so dtex = denier × 10/9 and denier = dtex × 0.9. The calculator converts your value into denier first and then into the target unit.
The principle
Weighing a known length is far easier and more reliable than measuring the diameter of a soft, compressible fibre. Mass per length depends on cross-sectional area and material density, so for the same material a higher number means a thicker yarn. Denier comes from an old silk trade unit (a 9,000 m skein). Tex was introduced as a metric, decimal system and is the system standardised by ISO; dtex is popular for synthetic filaments because it gives numbers close to denier. Note that indirect systems such as cotton count (Ne) and metric count (Nm) work the opposite way: higher numbers mean finer yarn.
Worked example
Default input: 70 denier to decitex.
- 70 denier means 70 g per 9,000 m.
- Scale to 10,000 m: 70 × 10,000 / 9,000 = 70 × 1.111111… = 77.77777778 dtex.
- In tex: 70 / 9 = 7.777777778 tex.
The calculator shows 77.77777778 dtex, and in everyday use you would write about 77.8 dtex (often rounded to 78 dtex on spec sheets).
How to read the result
Bigger numbers mean heavier, thicker yarn of the same material. Very fine microfibres are below about 1 dtex per filament, sheer stockings are often 10–20 denier, and tough outdoor fabrics commonly use 70D to 1000D nylon. A specification like 70D/24F means the 70-denier yarn is made of 24 filaments, so each filament is about 2.9 denier. Because density differs between materials, the same denier in polyester and nylon does not give exactly the same diameter.
Common mistakes
- Treating denier as a diameter. It is mass per length; diameter also depends on material density.
- Mixing direct systems (denier, tex) with indirect counts (Ne, Nm), which run in the opposite direction.
- Confusing yarn denier with fabric weight in g/m², which also depends on weave density.
Frequently asked questions
How many dtex is 70 denier?
About 77.8 dtex (70 × 10/9).
How do I convert tex to denier?
Multiply by 9. For example, 10 tex is 90 denier.
Is a higher denier fabric always stronger?
Usually a heavier yarn is more abrasion resistant, but weave and fibre type matter just as much, so compare similar fabrics only.
Sources: ISO 1144, Textiles — Universal system for designating linear density (Tex System) · BIPM, The International System of Units (SI Brochure), 9th edition