Yarn Tool
Twist Multiplier and TPI Calculator
Calculate turns per inch (TPI) from the twist multiplier and yarn count. Typical multipliers: 3.0 to 3.8 for knitting, 3.8 to 4.5 for weaving warp.
Formula: TPI = TM times the square root of Ne. TPM = TPI times 39.37. Related: Yarn count converter.
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Twist multiplier is the constant that links count to twist: TM = TPI ÷ √count. It lets you compare twist levels fairly across different counts, which raw TPI cannot do.
A 20s at 18 TPI and a 40s at 25 TPI sound very different, but both are around TM 4.0 — the same twist character.
Choosing TM by end use
| End use | TM | Character |
|---|---|---|
| Hosiery / knitting | 2.5 – 3.5 | Soft, bulky, low torque |
| Weft for weaving | 3.0 – 3.5 | Moderate strength, soft handle |
| Warp for weaving | 4.0 – 4.5 | Strong enough for sizing and loom stress |
| Denim warp | 4.2 – 4.8 | High strength for rope dyeing |
| Voile / crepe | 5.0 – 6.5 | Hard, dry, crisp handle |
The strength peak
Yarn strength does not rise indefinitely with twist. It climbs to a maximum around TM 4.5 to 5.0 for cotton, then falls as the fibre angle becomes too steep to contribute along the yarn axis.
Voile yarns sit deliberately past that peak. They trade strength for the dry, crisp handle that defines the fabric.
Frequently asked questions
What is twist multiplier?
The constant linking twist to count: TM equals TPI divided by the square root of the count. It allows fair comparison of twist across different counts.
What TM should I use for knitting yarn?
Between 2.5 and 3.5 for hosiery and knitting. Lower twist keeps the fabric soft and reduces spirality.
What TM is used for weaving warp?
Typically 4.0 to 4.5, rising to 4.8 for denim warp that must survive rope dyeing and high loom tension.
At what twist is cotton yarn strongest?
Around TM 4.5 to 5.0. Beyond that, strength falls again because the fibres lie at too steep an angle.
Can you supply yarn at a specified TM?
Yes. Give us the count, blend and target TM and we will match it from mill and confirm on test.