"Size 40 thread" can mean three different threads, depending on who says it. Thread is not sized by its diameter - a soft, hairy thread is hard to measure with a gauge - but by the relation between length and weight, which is easy and accurate to measure.
Two families of systems
| Family | Measures | Bigger number means | Systems |
|---|---|---|---|
| Direct (fixed length) | Weight of a fixed length | Thicker thread | Tex, dtex, denier |
| Indirect (fixed weight) | Length in a fixed weight | Finer thread | Cotton count (Ne), metric count (Nm), ticket number, embroidery weight |
This is the main source of confusion: Tex 40 is coarser than Tex 25, but Ne 40 is finer than Ne 25.
The systems one by one
- Tex - grams per 1,000 m. Tex 25 = 1 km weighs 25 g. ISO recommends Tex because it measures the whole finished thread, plies included. dtex = grams per 10,000 m (= Tex × 10).
- Denier - grams per 9,000 m. Used for filament yarns (polyester, nylon, rayon). Denier = Tex × 9. Embroidery thread "120/2" means two plies of 120 denier = 240 denier.
- Cotton count (Ne) - number of 840-yard hanks in one pound. Written per ply: 50/2 = two plies of Ne 50, which weighs the same as a single Ne 25.
- Metric count (Nm) - kilometres per kilogram. Nm = 1,000 ÷ Tex.
- Ticket number - a commercial label printed on cones; it is roughly 3 × the metric count of the finished thread (≈ 3,000 ÷ Tex). Ticket 120 ≈ Tex 25, ticket 80 ≈ Tex 35-40.
- Embroidery "weight" (wt) - km per kg of the whole thread. 40 wt = Tex 25 = 225 denier.
Conversion formulas
| From → To | Formula |
|---|---|
| Denier → Tex | Tex = Denier ÷ 9 (× 0.111) |
| Tex → Denier | Denier = Tex × 9 |
| Ne (cotton count) → Tex | Tex = 590.5 ÷ Ne |
| Tex → Ne | Ne = 590.5 ÷ Tex |
| Nm → Tex | Tex = 1,000 ÷ Nm |
| Weight (wt) → Tex | Tex = 1,000 ÷ wt |
| Weight (wt) → Denier | Denier = 9,000 ÷ wt |
| Ne plied (e.g. 50/2) → resultant Ne | 50 ÷ 2 = Ne 25 → Tex ≈ 23.6 |
Formula: 40 wt = Tex 25 = 225 denier = Nm 40
Which thread for which fabric
A general guide by fabric weight (always confirm with your thread supplier and the buyer's standard):
| Fabric weight (g/m²) | Typical fabrics | Thread size |
|---|---|---|
| 65 - 135 | Voile, poplin, light jersey | Tex 16 - 24 |
| 135 - 200 | Shirting, single jersey, interlock | Tex 24 - 30 |
| 200 - 270 | Twill, light denim, fleece | Tex 30 - 50 |
| 270 - 340 | Drill, medium denim | Tex 40 - 60 |
| 340 - 475 | Heavy denim, canvas, workwear | Tex 60 - 135 |
Needle size
As a rule the needle eye should be about 40% larger than the thread. Tex 25 (40 wt) usually runs on Nm 75-80 (size 11-12); a heavier Tex 30-35 needs Nm 90-100 (size 14-16). A thicker thread also pushes the tension discs apart, so re-check tension whenever you change thread size.
Avoiding mistakes in tech packs
- Always write the system name with the number: "Tex 27", never just "27".
- For cotton count always give the ply: "Ne 40/2".
- Use one system through the whole tech pack - Tex if possible.
- Do not confuse cotton count with ticket number, or metric count with metric ticket.
- When in doubt, send a physical thread sample with the order.