EPI and PPI in Woven Fabrics: What They Mean and Why They Matter

Every woven fabric is made of two sets of yarns that interlace at right angles. The warp threads run lengthwise — parallel to the selvedge, along the length of the loom. The weft threads (also called filling threads) run crosswise — perpendicular to the selvedge, across the width of the fabric.

EPI and PPI describe how many warp yarns and weft yarns, respectively, fit within one inch of fabric. These two numbers together form the thread count of a woven fabric — the primary measure of its construction density.

EPI stands for Ends Per Inch. It is the count of warp yarns (called "ends") present in one inch of fabric measured across the fabric width. A higher EPI means more warp yarns are packed per inch, producing a denser, typically stronger fabric with a finer appearance.

To measure EPI, a pick glass or thread counter is placed on the fabric and the warp threads visible within one inch are counted. In production, EPI is set on the loom at the point of weaving and is a controlled parameter — it directly reflects the loom setup.

Common EPI values vary significantly by fabric category. Basic plain-weave shirtings typically run at 60 EPI. Fine poplin or percale constructions may reach 100–120 EPI or higher. Canvas and heavier utility fabrics often use 30–40 EPI with heavier yarns. The EPI figure must always be read alongside the yarn count — a higher EPI with a coarser yarn produces a very different fabric than the same EPI with fine yarn.

EPI is a warp property. It describes the density of threads running along the length of the roll. It does not, by itself, tell you anything about the weft.

PPI stands for Picks Per Inch. It is the count of weft yarns (called "picks") present in one inch of fabric measured along the fabric length. Each pick is one weft thread that has been passed (or "picked") across the loom from selvedge to selvedge.

A higher PPI means more weft threads are packed per inch of fabric length. This generally produces a heavier, denser fabric with more cover. Like EPI, PPI affects weight, texture, drape, and hand feel — a high-PPI fabric tends to be firmer and less drapy than a low-PPI fabric with the same warp.

PPI is controlled by the beat-up mechanism of the loom — how forcefully each inserted weft thread is pushed into position against the previously inserted threads. It can be measured in finished fabric by counting picks with a thread counter across one inch of length.

Common PPI values roughly mirror EPI values for balanced constructions. A 60 × 60 fabric has 60 EPI and 60 PPI — equal warp and weft density. Higher or lower PPI relative to EPI produces an unbalanced construction with different properties in the warp and weft directions.

The combined EPI × PPI value — written as a pair such as 60 × 60 or 100 × 80 — describes the full construction density of the woven fabric. It is used in technical specifications, quality audits, procurement documents, and sample records as the primary construction identifier alongside yarn count and weave structure.

A balanced construction (equal EPI and PPI, such as 60 × 60) produces a fabric with similar strength and appearance in both directions. Balanced plain weaves are the most common construction in commodity shirtings and basic apparel fabrics.

A warp-dominant construction (high EPI relative to PPI, such as 100 × 60) means more warp yarns per inch than weft. The fabric's appearance and properties are driven more by the warp yarn. Many fine poplins and broadcloths are warp-dominant.

A weft-dominant construction (high PPI relative to EPI) is less common but produces specific drape and texture effects valued in certain decorative or technical fabrics.

In SampleLedger, EPI and PPI are stored as separate fields and automatically combined into the epiPpi display value (for example, "60 × 60") that appears on sample records and stickers. Storing them separately allows filtering and search by either value independently.

The relationship between thread count and fabric properties is not perfectly linear — yarn count, weave structure, and finishing all play a role — but the following patterns hold broadly across woven constructions:

Higher combined count (high EPI and PPI): denser, heavier fabric with better cover; smoother surface; generally stronger; finer appearance; higher cost per metre due to more yarn consumed and slower weaving speed. Fine poplin (80 × 80 or higher in fine yarns) is a clear example — dense, smooth, crisp.

Lower combined count (low EPI and PPI): more open weave with visible structure; lighter and more economical; often with a softer hand and better breathability. Cheesecloth and open-weave gauze sit at this extreme. Mid-range canvas weaves (30 × 28 in heavy yarns) are open but sturdy.

Imbalanced count: directional differences in strength, stretch, and appearance. A twill weave at 70 × 40 will behave very differently along the warp than along the weft — the warp direction is much denser. This affects how the fabric behaves when cut on the bias or stressed in different directions.

Three practical examples: a standard shirting poplin at 60 × 60 in 40s yarn is balanced, smooth, and lightweight; a 3/1 twill denim at 72 × 42 in heavy yarn is warp-dominant, sturdy, with a pronounced diagonal rib; a plain-weave canvas at 32 × 28 in coarse yarn is open and robust. Each has a distinct EPI × PPI profile that explains its properties.

EPI and PPI belong on every woven fabric sample record. Without them, a specification sheet is incomplete — two fabrics can have identical GSM, identical yarn counts, and even identical weave names, but very different properties if their thread densities differ. The EPI × PPI combination is what distinguishes one 60s poplin from another.

SampleLedger stores EPI and PPI as individual numeric fields on each sample record. The combined value is derived automatically and displayed as epiPpi — for example, "72 × 60" — on stickers and spec pages. This gives buyers and production teams both the raw numbers and the combined notation without manual calculation. You can read more about how construction fields are managed in the fabric sample tracking features page.