Convert Turns per Centimeter to Turns per Inch (TPcm to TPI)
1 turn per centimetre (TPcm) = 2.54 turns per inch (TPI). 1 TPI = 0.3937007874 TPcm. Example: 4 TPcm = 4 × 2.54 = 10.16 TPI.
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1 TPcm = 2.54 TPI
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk turn per centimetre to turn per inch converter to paste a column from Excel.
How to Convert Turn per Centimeter to Turn per Inch
- 1 TPcm = 2.54 TPI
- 1 TPI = 0.3937007874 TPcm
- Example: convert 4 TPcm to TPI: 4 TPcm = 4 × 2.54 TPI = 10.16 TPI
Formula
TPI = TPcm × 2.54
Derivation from SI units:
- 1 turn per cm = 100 turns per metre
- 1 TPI = 1 turn per 0.0254 m = 39.37007874 TPM (exact)
- 1 TPcm = 100 TPM ÷ 39.37007874016 TPM per TPI = 2.54 TPI
Both units are defined exactly, so the factor is exact. Turn per Centimeter definition: turn per centimetre; Turn per Inch definition: turn per inch.
Worked examples
- A ply yarn with 4 TPcm has 10.16 TPI.
4 TPcm × 2.54 = 10.16 TPI - A yarn with 8 TPcm has 20.32 TPI.
8 TPcm × 2.54 = 20.32 TPI
Turn per Centimeter to Turn per Inch conversion table
| Turns per Centimeter (TPcm) | Turns per Inch (TPI) |
|---|---|
| 1 TPcm | 2.54 TPI |
| 2 TPcm | 5.08 TPI |
| 3 TPcm | 7.62 TPI |
| 4 TPcm | 10.16 TPI |
| 5 TPcm | 12.7 TPI |
| 6 TPcm | 15.24 TPI |
| 8 TPcm | 20.32 TPI |
| 10 TPcm | 25.4 TPI |
| 12 TPcm | 30.48 TPI |
| 15 TPcm | 38.1 TPI |
Where it's used
Twist in turns per centimetre from tester printouts is converted to turns per inch for cotton-system twist multipliers and US specifications. Multiply by 2.54.
Turn per Centimeter to other yarn twist units
| Conversion | 1 TPcm equals |
|---|---|
| turn per centimetre to turn per inch | 2.54 TPI |
| turn per centimetre to turn per metre | 100 TPM |
| turn per centimetre to turn per foot | 30.48 TPF |
Frequently asked questions
How do I convert turns per cm to TPI?
Multiply by 2.54: 4 turns/cm = 10.16 TPI.
How many turns per inch are in 1 turn per centimetre?
1 TPcm = 2.54 TPI.
How do I convert turns per centimetre to turns per inch?
Multiply the value in TPcm by 2.54. For example, 4 TPcm × 2.54 = 10.16 TPI.
Is the TPcm to TPI conversion exact?
Yes. Both units are defined exactly, and 1 TPcm is exactly 2.54 TPI.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
- Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology , Appendix B.8, "inch".
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Convert Turns per Centimeter to Turns per Inch (TPcm to TPI). Retrieved October 25, 2026, from https://scientificconverters.com/yarn-twist/turns-per-centimeter-to-turns-per-inch/
IEEE
Scientific Converters, "Convert Turns per Centimeter to Turns per Inch (TPcm to TPI)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/yarn-twist/turns-per-centimeter-to-turns-per-inch/