AA Enterprises · Buyer Tools
Yarn Diameter & Maximum Sett Calculator
Estimate yarn diameter and the maximum sett (threads per inch) from the cotton count.
Ashenhurst: diameter (inch) ≈ 1 ÷ (28√Ne); maximum sett (threads touching) ≈ 28√Ne. Practical setts are roughly 60–90% of the maximum depending on weave.
Need this quantity quoted?
Send your count, blend and quantity and we will come back with firm pricing ex-Delhi and a lead time, within one working day.
Get a quote Ask on WhatsAppEstimating yarn diameter from count
Yarn diameter is not usually measured directly — it is estimated from count, because yarn is compressible and its apparent diameter changes with the pressure you apply.
The common approximation for cotton is that diameter in inches is roughly 1 ÷ (28 × √Ne). Finer counts give smaller diameters, and the square root relationship means halving the diameter needs four times the count.
Approximate diameters
Maximum sett is the theoretical thread density where yarns just touch with no space between them. Real fabrics weave at 60 to 90 per cent of maximum sett, depending on the weave.
| Count (Ne) | Diameter (mm) | Ends per inch at max sett |
|---|---|---|
| 10s | 0.29 | 88 |
| 20s | 0.20 | 125 |
| 30s | 0.17 | 153 |
| 40s | 0.14 | 177 |
| 60s | 0.12 | 216 |
| 80s | 0.10 | 250 |
Why sett matters more than diameter
Diameter is mainly useful as a route to sett — how many threads per inch a fabric can physically hold. Plain weave, with its maximum interlacing, typically works at around 60 to 70 per cent of maximum sett. Twill can go higher, around 75 to 85 per cent, because it has fewer interlacings per unit area.
Getting this wrong is why some constructions simply cannot be woven at the density the designer specified.
Frequently asked questions
How do I calculate yarn diameter from count?
For cotton, diameter in inches is approximately 1 divided by (28 times the square root of Ne). A 30s yarn is roughly 0.17 mm.
What is maximum sett?
The theoretical thread density at which yarns just touch with no gaps. Real fabrics weave at 60 to 90 per cent of it.
Why can twill be woven tighter than plain weave?
Twill has fewer interlacings per unit area, so the yarns can pack closer before the fabric jams.
Is yarn diameter measured or calculated?
Almost always calculated from count. Yarn compresses under measurement, so a direct reading depends heavily on the pressure applied.
Can you recommend a count for my sett?
Yes. Send your target EPI and weave and we will suggest counts that weave cleanly at that density.