Unit Converters

Cm to inches converter.

Type centimetres or inches and the other box updates as you type. One inch is exactly 2.54 cm, so inches = cm ÷ 2.54. Runs in your browser; nothing is sent anywhere.

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Result

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Answer

30 cm is 11.811 in. 1 in = 2.54 cm exactly, so 1 cm = 0.393700787… in.

Formula

inches = cm ÷ 2.54

Take 30 cm. inches = cm ÷ 2.54 gives 11.811 in. Going back: 11.811 in converts back to 30 cm.

Quick estimate: multiply cm by 0.4 (slightly high), then nudge down a little.

Cm to inches table (1 to 100)

Centimetres (cm)	Inches (in)
1	0.3937
2	0.7874
3	1.1811
4	1.5748
5	1.9685
6	2.3622
7	2.7559
8	3.1496
9	3.5433
10	3.937
15	5.9055
20	7.874
25	9.8425
30	11.811
40	15.748
50	19.685
60	23.622
70	27.5591
75	29.5276
80	31.4961
90	35.4331
100	39.3701

Examples

10 cm = 3.937 in
30 cm = 11.811 in
50 cm = 19.685 in
100 cm = 39.3701 in

Source

Conversion factors and formulas: NIST SP 811, Appendix B.8: inch to centimeter, 2.54 E+00; NIST Handbook 44 (2026), Appendix C: 1 inch = 2.54 cm. Retrieved 2026-10. Results are rounded for display to 4 decimal places; the arithmetic itself is not rounded.

FAQ

How many inches are in 1 centimetre?

1 cm is 0.393701 in. 1 in = 2.54 cm exactly, so 1 cm = 0.393700787… in.

What is the formula to convert centimetres to inches?

inches = cm ÷ 2.54. For 30 cm that gives 11.811 in.

Is the conversion factor exact?

Yes for the stated definition. 1 in = 2.54 cm exactly, so 1 cm = 0.393700787… in. The tool shows results rounded to four decimal places; the underlying arithmetic is not rounded.

How do I estimate it in my head?

Quick estimate: multiply cm by 0.4 (slightly high), then nudge down a little. Use the exact factor when accuracy matters.

What is 50 cm in inches?

50 cm is 19.685 in.

Disclaimer

Informational arithmetic using the published factors above. For legal-for-trade, engineering or medical use, check against the governing standard.