Yarn count calculator

What each number is

• Count (Ne)English cotton count: how many 840-yard hanks weigh a pound. Higher is finer. A heavy tweed is Ne 2–3, a kilt worsted about Ne 5, a shirting poplin Ne 40, a voile Ne 80.
• TexThe metric way round — grams per 1000 metres, so higher is coarser. tex = 590.5 / Ne.
• DiameterHow thick the yarn is before it is squashed into the cloth, from Peirce's rule 25.4 / (28 √Ne) mm. In cloth a spun yarn lies about twice as wide as this.
• Wraps per inchHow many turns of the yarn fill an inch of a ruler — the measurement a hand weaver can take without any arithmetic. 28 √Ne.
• SettEnds per inch at which the flattened yarn just fills its own pitch: 14 √Ne, times openness. This is the closed sett; set it more openly for a voile or a gauze.
• OpennessHow loosely you mean to set it, 0.5 to 1. A cotton voile is about 0.74; 1 closes the cloth.
• CoverHow much of the sett the yarn fills. Below 100% the cloth is open and the ground shows through. A closed cloth can read 99% simply because ends per inch is a whole number: Ne 5.3 closes at 32.2 and the loom can only be threaded at 32.

Two of the studio's own cloth presets land on this arithmetic exactly: kilt worsted at Ne 5.3 gives 32 ends per inch, and 64 threads of it measure 5.1 cm; shirting poplin at Ne 40 gives 89, and the same 64 threads measure 1.8 cm. Those are the figures the app prints.

Two directions are useful. Given a yarn, the sett follows — that is the default. Given a sett you already weave at, the balanced count follows: Ne = (epi / 14)². Type into the sett box and the count above changes to the one that closes that cloth.

Why the sett matters for a design, not just a loom

A thread count is in threads, so on its own it says nothing about size. The yarn is what turns it into centimetres: sixty-four threads at Ne 5.3 is a different cloth from sixty-four threads at Ne 40, and only one of them is a shirt. This is also why a pattern exported without a physical size is guesswork for whoever receives it.