AiVibe

Textile & Automotive Manufacturing

Ends per Inch and Picks per Inch (EPI, PPI)

Ends per inch (EPI) and picks per inch (PPI) give the thread density of a woven fabric: the number of warp yarns and weft yarns per inch, or per centimetre. With yarn counts, they define a fabric's construction.

EPI counts warp ends across a unit width and PPI counts weft picks along a unit length. A woven fabric construction is commonly written as warp count by weft count over EPI by PPI, for example 40s x 40s / 133 x 72 for a cotton fabric described in Ne. In bed linen, thread count usually refers to the sum of warp and weft threads per square inch.

Thread density, together with yarn count and weave, determines fabric weight, cover, strength, air permeability and handle, so it is a core part of fabric specifications between buyers, weavers and processors. On the loom, the reed count and the number of ends per dent set the warp density, while the take-up motion sets the pick density.

Densities change between the loom, the grey fabric and the finished fabric because of shrinkage and stretching in processing, so the state of the fabric must be stated. Thread density is measured with a counting glass or by image analysis, and ISO 7211-2 describes methods for determining the number of threads per unit length. Variation in pick density appears as defects such as thick and thin places or starting marks.

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Where AiVibe comes in

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