# How do I convert cm to inches?

Converts centimeters (cm) to inches (in) and back, with the exact unit definitions.

- Page: https://www.acalculator.org/convert/cm-to-inches
- JSON spec: https://www.acalculator.org/convert/cm-to-inches.json
- Version: d0df0c89dea4

## Default answer

Example with the default inputs (Centimeters (cm) 1): 1 cm = 0.393701 in.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| value | Centimeters (cm) | The amount in centimeters to convert. |
| result | Inches (in) | The same amount in inches. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| value | Centimeters (cm) | The amount in centimeters to convert. |
| result | Inches (in) | The amount in inches. |
| fraction | Nearest 1/64 inch | The length in inches rounded to the nearest 1/64 inch, as on a tape measure. |

## Method

in = cm × 0.393700787402 (the same as cm ÷ 2.54)

## Assumptions

- 1 centimeter = 0.393700787402 inches, from the exact definitions in NIST SP 811.
- The answer shows at most 6 decimal places; the calculation keeps full precision.

## Worked examples

1. value = 1 gives result = 0.393701. Source: exact unit definitions in NIST SP 811 (2008), Appendix B.8.
2. value = 30 gives result = 11.811024. Source: exact unit definitions in NIST SP 811 (2008), Appendix B.8.
3. result = 11.811024 gives value = 30. Source: exact unit definitions in NIST SP 811 (2008), Appendix B.8.

## FAQ

### How many inches are in a centimeter?

1 centimeter is 0.393701 inches, from the exact unit definitions (NIST SP 811).

### How do I convert cm to inches?

Multiply by 0.393701: in = cm × 0.393700787402 (the same as cm ÷ 2.54). For example, 1 cm × 0.393701 = 0.393701 in.

### How do I convert inches back to cm?

Multiply by 2.54, or type the inches into the second box and the converter works it out. 1 inch is 2.54 centimeters.

## Sources

- NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B.8. https://www.nist.gov/pml/special-publication-811