Convert Turns per Inch to Turns per Centimeter (TPI to TPcm)
1 turn per inch (TPI) = 0.3937007874 turns per centimetre (TPcm). 1 TPcm = 2.54 TPI. Example: 10 TPI = 10 × 0.3937007874 = 3.937007874 TPcm.
Also searched as turns per inch to TPcm, turns per inch in TPcm, turns per inch into turns per centimetre, TPI to TPcm, TPI in turns per centimetre, TPI into turn per centimetre, turn per inch to turn per centimetre, TPI to turns per centimetre converter, turns per inch to turns per centimeter and how many turns per centimetre in a turn per inch.
1 TPI = 0.3937007874 TPcm
Type in either box. Scientific notation works: 1.5e-3.
Converting a list? Use the bulk turn per inch to turn per centimetre converter to paste a column from Excel.
How to Convert Turn per Inch to Turn per Centimeter
- 1 TPI = 0.3937007874 TPcm
- 1 TPcm = 2.54 TPI
- Example: convert 10 TPI to TPcm: 10 TPI = 10 × 0.3937007874 TPcm = 3.937007874 TPcm
Formula
TPcm = TPI × 0.3937007874016
or TPcm = TPI ÷ 2.54
Derivation from SI units:
- 1 TPI = 1 turn per 0.0254 m = 39.37007874 TPM (exact)
- 1 turn per cm = 100 turns per metre
- 1 TPI = 39.37007874016 TPM ÷ 100 TPM per TPcm = 0.3937007874016 TPcm
Both units are defined exactly, so the factor is exact. Turn per Inch definition: turn per inch; Turn per Centimeter definition: turn per centimetre.
Worked examples
- A yarn with 10 TPI has 3.937007874 TPcm.
10 TPI × 0.3937007874 = 3.937007874 TPcm - A fine yarn with 20 TPI has 7.874015748 TPcm.
20 TPI × 0.3937007874 = 7.874015748 TPcm
Turn per Inch to Turn per Centimeter conversion table
| Turns per Inch (TPI) | Turns per Centimeter (TPcm) |
|---|---|
| 3 TPI | 1.181102362 TPcm |
| 5 TPI | 1.968503937 TPcm |
| 8 TPI | 3.149606299 TPcm |
| 10 TPI | 3.937007874 TPcm |
| 12 TPI | 4.724409449 TPcm |
| 15 TPI | 5.905511811 TPcm |
| 16.1 TPI | 6.338582677 TPcm |
| 18 TPI | 7.086614173 TPcm |
| 20 TPI | 7.874015748 TPcm |
| 25 TPI | 9.842519685 TPcm |
Where it's used
Twist in turns per inch is converted to turns per centimetre for laboratory twist testers and filament or ply twist records. Divide by 2.54.
Turn per Inch to other yarn twist units
| Conversion | 1 TPI equals |
|---|---|
| turn per inch to turn per centimetre | 0.3937007874 TPcm |
| turn per inch to turn per metre | 39.37007874 TPM |
| turn per inch to turn per foot | 12 TPF |
Frequently asked questions
How many turns per cm is 10 TPI?
10 TPI = 3.937007874 TPcm, since 1 inch = 2.54 cm exactly.
How many turns per centimetre are in 1 turn per inch?
1 TPI = 0.3937007874 TPcm.
How do I convert turns per inch to turns per centimetre?
Multiply the value in TPI by 0.3937007874, or divide it by 2.54. For example, 10 TPI × 0.3937007874 = 3.937007874 TPcm.
Is the TPI to TPcm conversion exact?
Yes. Both units are defined exactly, so the ratio is exact; its decimal form does not terminate and is shown here to 10 significant figures (more with the precision selector).
Sources
- 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".
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
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 Inch to Turns per Centimeter (TPI to TPcm). Retrieved October 25, 2026, from https://scientificconverters.com/yarn-twist/turns-per-inch-to-turns-per-centimeter/
IEEE
Scientific Converters, "Convert Turns per Inch to Turns per Centimeter (TPI to TPcm)," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/yarn-twist/turns-per-inch-to-turns-per-centimeter/