AA Enterprises · Buyer Tools
Twist (TPI) Calculator
Work out yarn twist per inch and per metre from the count and twist multiplier.
TPI = twist multiplier × √count (Ne). Typical TM: warp ~4.0–4.5, weft ~3.0–3.5, hosiery ~2.5–3.5. TPM = TPI × 39.37.
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Twist multiplier (TM), sometimes written as the twist factor, is the number that links yarn count to the amount of twist inserted. The higher the TM, the more turns per inch for a given count, and the harder and stronger the yarn feels.
Choosing TM is a trade-off. More twist gives strength and a crisper handle but a harsher feel and more torque, which can cause spirality in knitted fabric. Less twist gives softness and bulk but a weaker yarn that sheds more during processing.
| Application | Typical TM | Why |
|---|---|---|
| Warp yarn for weaving | 4.0 – 4.5 | Must survive sizing, beaming and repeated loom abrasion |
| Weft yarn for weaving | 3.0 – 3.5 | Less stress in use, so softer yarn is acceptable |
| Hosiery and knitting | 2.5 – 3.5 | Low twist keeps fabric soft and reduces spirality |
| Voile and high-twist fabric | 5.0 – 6.0 | Deliberately hard twist for a dry, crisp handle |
| Weaving yarn for denim warp | 4.2 – 4.8 | Needs strength for rope dyeing and high loom tension |
How TPI and TPM relate
TPI (twists per inch) and TPM (twists per metre) describe the same thing in different units. One inch is 0.0254 metres, so TPM equals TPI multiplied by 39.37.
TPI itself is derived from the count and the twist multiplier: TPI = TM × √count (Ne). Because count sits under a square root, finer yarns need proportionally more turns per inch to reach the same TM.
Worked example
Take 30s Ne combed cotton for a knitted T-shirt. A hosiery TM of 3.4 is typical. The square root of 30 is 5.477, so TPI = 3.4 × 5.477 = 18.6. Converting to metric, TPM = 18.6 × 39.37 = 733.
If the same 30s were being used as weaving warp at TM 4.2, TPI would rise to 23.0 and TPM to 906 — roughly a quarter more twist for the same count.
Frequently asked questions
What is a good twist multiplier for cotton yarn?
It depends on end use. Knitting and hosiery yarn typically runs TM 2.5 to 3.5, weft yarn 3.0 to 3.5, and weaving warp 4.0 to 4.5. High-twist fabrics such as voile can go to 5.0 or above.
How do I convert TPM to TPI?
Divide TPM by 39.37. For example 800 TPM divided by 39.37 gives 20.3 TPI. To go the other way, multiply TPI by 39.37.
Does higher twist make yarn stronger?
Up to a point. Strength rises with twist until it reaches an optimum, then falls again as the fibres become so steeply angled that they contribute less along the yarn axis. That optimum is usually around TM 4.5 to 5.0 for cotton.
Why does twist cause spirality in knitwear?
Residual torque in a high-twist single yarn makes the loops lean, so the fabric skews after washing. Lower twist, a two-fold yarn, or steam setting all reduce it.
Can you supply yarn to a specific TPI?
Yes. Tell us the count, blend and target TM or TPI and we will match it from mill. Twist is one of the parameters we specify on every order.