Centimeters to Inches
Convert centimeters (cm) to inches (in). Both measure distance and dimension, and the conversion comes up in construction, navigation, sports work.
The Formula
``
inches = centimeters × 0.393700787402
centimeters = inches × 2.54
`
One centimeter is 0.393701 inches, and one inch is 2.54 centimeters.
Conversion Table
| Centimeters | Inches |
|---|---|
| 1 cm | 0.393701 in |
| 2 cm | 0.787402 in |
| 5 cm | 1.9685 in |
| 10 cm | 3.937 in |
| 25 cm | 9.8425 in |
| 50 cm | 19.685 in |
| 100 cm | 39.3701 in |
| 500 cm | 196.8504 in |
| 1,000 cm | 393.7008 in |
The Other Direction
| Inches | Centimeters |
|---|---|
| 1 in | 2.54 cm |
| 2 in | 5.08 cm |
| 5 in | 12.7 cm |
| 10 in | 25.4 cm |
| 25 in | 63.5 cm |
| 50 in | 127 cm |
| 100 in | 254 cm |
| 500 in | 1,270 cm |
| 1,000 in | 2,540 cm |
What Each Unit Is
Centimeters (cm) — one hundredth of a metre. A metric subdivision, and the everyday unit for body and object measurements in metric countries.
Inches (in) — exactly 2.54 centimetres — an exact figure, not a rounded one. From the Latin uncia, one twelfth (of a foot); the exact metric value was agreed in 1959.
A Sense of Scale
A fingernail is about 1 cm wide- A credit card is 8.6 cm long
- A4 paper is 21 cm wide
- A thumb is about an inch wide
- Screens are measured diagonally in inches
- US rainfall is in inches
Doing It in Your Head
Multiply by 2, then divide by 5. That is off by 1.60% — close enough to judge a
distance, a weight or a price, and not close enough to sign off on a drawing.
Exact Mental shortcut 3.937 in 4 in 39.3701 in 40 in
Precision
The factor 0.393700787402 is exact by international agreement, not a rounded approximation. Any imprecision in a result comes from your input, not the conversion.
Watch Out For
- Because the inch is exactly 2.54 cm, inch↔cm conversions are exact and any rounding you see comes from your own input precision, not the factor.
In Code
`javascript
const centimeterToInch = (value) => value * 0.393700787402;
``
Where This Conversion Comes Up
- Construction
- Navigation
- Sports
- Sewing
- Mapping
How Many Decimals Do You Need?
Rounding the factor costs accuracy, and how much depends on the factor. Converting 137 cm with the factor truncated at each decimal place:
| Decimals kept | Factor | 137 cm becomes | Error |
|---|---|---|---|
| 0 | 0 | 0 | 100.0000% |
| 1 | 0.4 | 54.8 | 1.6000% |
| 2 | 0.39 | 53.43 | 0.9400% |
| 3 | 0.394 | 53.978 | 0.0760% |
| 4 | 0.3937 | 53.9369 | 0.0002% |
The right number of significant figures is set by your input, not by the converter. If you measured centimeters to three significant figures, the answer in inches is only good to three — writing more digits claims precision the measurement never had.