Denier

Denier (abbreviated as D or den) is a unit that measures the fineness of fibers and yarns by expressing their linear mass density—specifically, the weight in grams of 9,000 meters of the fiber or yarn. A single strand of silk, the historical reference point for this measurement, weighs approximately 1 gram per 9,000 meters, giving it a denier of 1.

The formula is straightforward: Denier = (Mass in grams ÷ Length in meters) × 9,000. Lower denier values indicate finer, lighter fibers, while higher values indicate coarser, heavier ones. This relationship makes denier particularly useful for predicting fabric characteristics—finer fibers generally produce softer hand feel and more fluid drape.

Microfiber is defined as any fiber with a denier below 1, which explains its exceptionally soft texture and high surface area. These ultra-fine fibers can be split or shaped to enhance specific properties like moisture-wicking or cleaning ability.

A related measurement, decitex (dtex), expresses mass in grams per 10,000 meters and is commonly used in European specifications. The conversion is simple: Denier = Dtex × 0.9. When reviewing international specifications, buyers should verify which unit is being used to ensure accurate comparisons. Denier specifications work alongside thread count and GSM to give a complete picture of fabric construction and weight.