How Woven Fabric Is Made: Ends, Picks and Yarn Count
Every woven fabric is described, in the end, by a few numbers: how many warp threads per inch, how many weft threads per inch, and how thick those threads are. Those numbers are decided long before the cloth reaches a shop, at the stages where yarn is wound onto a beam, threaded through the loom, and woven. This guide walks through how woven fabric is made, step by step, and shows how each stage fixes one of the figures you will see on a spec sheet. Worked examples use the site's Thread Count & Cover Factor Calculator and yarn count converter.
Warp and weft
Weaving interlaces two sets of yarn at right angles. The warp runs the length of the fabric and is held under tension on the loom. The weft is inserted across the warp, one pick at a time. The finished fabric is described by the density of each:
- Ends per inch (EPI) or per centimetre: the number of warp yarns across the width.
- Picks per inch (PPI) or per centimetre: the number of weft yarns along the length.
Thread count is EPI plus PPI, and the warp-to-weft balance is EPI divided by PPI. Both come straight out of the loom set-up.
Step 1: preparing the warp
Warp yarns have the hardest life in weaving. They are held under tension, rubbed by the loom's moving parts, and lifted and lowered thousands of times. So they are prepared carefully:
- Warping: thousands of yarns are wound side by side, at even tension, onto a large roller called the warp beam. The number of yarns is the total number of ends in the fabric, which is the EPI times the width in inches, plus a few extra for the selvedges.
- Sizing: spun yarns, such as cotton, are usually coated with a size, a starch or synthetic film that lays down loose fibres and strengthens the yarn for weaving. The size is washed out in finishing, which is one reason fabric off the loom is stiffer and heavier than the finished cloth.
- Drawing in: each warp end is threaded through an eye in a heddle, which lifts or lowers it, and through a gap in the reed, a comb-like part that spaces the yarns and beats each weft into place. The reed count, the number of gaps per unit width, together with how many ends pass through each gap, sets the EPI on the loom.
Step 2: weaving
Every loom, from a hand loom to a modern air-jet machine, repeats three motions:
- Shedding: the heddles lift some warp ends and lower others, opening a gap called the shed. Which ends go up decides the weave: alternate ends for plain weave, a stepped pattern for twill, widely spaced ends for satin.
- Picking: a weft yarn is carried across through the shed. Older looms throw a shuttle; modern looms use rapiers, a small projectile, or a jet of air or water.
- Beating up: the reed pushes the new pick against the woven fabric.
The rate at which the woven fabric is drawn forward, relative to the number of picks inserted, sets the PPI. Change the take-up and you change the picks per inch, and with it the weight and density of the cloth.
Step 3: finishing
Fabric straight off the loom, called greige or grey cloth, is rarely what you buy. Finishing can include desizing to remove the size, scouring and bleaching, dyeing or printing, mercerising cotton for lustre and strength, brushing or sanding for a soft surface, heat-setting synthetics, and mechanical pre-shrinking. Finishing changes the numbers: fabrics that shrink in finishing end up with more ends and picks per inch, and a higher GSM, than they had on the loom.
Ends, picks and yarn count together: three examples
Here are three classic fabric types, with constructions typical of the type, run through the thread count calculator:
| Fabric | Construction | Thread count | Balance | Cloth cover |
|---|---|---|---|---|
| Heavy canvas | 60 x 40, Ne 10 yarns | 100 | 1.5:1 | 23.05 |
| Drill | 80 x 60, Ne 20 yarns | 140 | 1.33:1 | 22.73 |
| Poplin | 133 x 72, Ne 40 yarns | 205 | 1.85:1 | 23.86 |
Look at the thread counts: 100, 140 and 205. Then look at the cover: all three sit in a narrow band around 23. The canvas has few threads, but each is thick; the poplin has many, but each is fine. Their densities in the sense that matters, how much of the area is covered by yarn, are similar. Thread count on its own would suggest the poplin is twice as dense as the canvas, which is not true.
The yarns are very different, though. In the yarn count converter, Ne 10 is 59.05 tex, Ne 20 is 29.53 tex, and Ne 40 is 14.76 tex. The canvas yarn is four times as heavy per metre as the poplin yarn, which is why the canvas is so much heavier and stiffer per square metre.
Crimp: why the yarn is longer than the fabric
Woven yarns do not lie straight. They bend over and under each other, so a metre of fabric contains more than a metre of each yarn. This extra length is called crimp, or take-up, and it is usually a few percent, sometimes more. Crimp is one reason that you cannot simply multiply yarn counts by ends and picks to get an exact fabric weight; the yarns are longer than the cloth. It also explains why a woven fabric stretches a little when pulled along the warp or weft: the crimp straightens out.
How the weave changes the numbers
- Plain weave has the most crossings, so it can hold the fewest threads per inch before it jams. It is stable and firm.
- Twill, with diagonal lines formed by floats over two or more threads, packs more threads and drapes better. Denim, drill, gabardine and chino are twills.
- Satin and sateen float over four or more threads, pack the most threads, and give a smooth, lustrous face.
The calculator's cover formula is most accurate for plain weaves and simple twills. For satins and sateens, it understates how closely the threads can pack, so compare like with like. The percale and sateen guide looks at that difference in detail.
Reading a weaving spec
A full woven fabric spec usually reads something like "100% cotton, plain weave, 40 x 40 / 133 x 72, 58 inch, 115 GSM". In order: fibre; weave; warp and weft counts; ends and picks per inch; width; weight. If the counts are in tex or dtex, convert them to Ne before using the thread count calculator. If the weight is in ounces, the Fabric Weight Converter gives GSM.
Counting ends and picks yourself
A magnifier with a scale, called a pick glass, lets you count threads on a sample. Count across one inch, or a fraction of an inch on fine cloth, in several places, and average. Fabric that has shrunk in washing will have more threads per inch than the mill quoted for the loom, so a count on washed cloth may not match a greige specification.
What the tools cover
The calculators turn ends, picks and yarn counts into thread count, balance and cover factor, and convert yarn counts between systems. They do not model crimp, yarn flattening, weave floats or finishing, so they cannot predict an exact fabric weight from the loom set-up. For production weaving, those come from trial weaves and the mill's own experience; for comparing fabrics as a buyer or maker, the numbers above are enough to see past a bare thread count.