Inches to centimeters
cm = in × 2.54
Exact factor: 1 in = 1/36 yd = 0.0254 m.
Centimeters to inches converter (and inches to cm)
Two-way centimeters ↔ inches converter: exact factor (1 in = 2.54 cm), formulas, a mental-math shortcut, a conversion table and real examples (TV diagonal, height in cm, A4 vs Letter paper, European bike frames).
Conversion table
| cm | in |
|---|---|
| 1 cm | 0.3937 in |
| 2 cm | 0.7874 in |
| 5 cm | 1.9685 in |
| 10 cm | 3.93701 in |
| 20 cm | 7.87402 in |
| 50 cm | 19.685 in |
| 100 cm | 39.3701 in |
| 1,000 cm | 393.701 in |
| in | cm |
|---|---|
| 1 in | 2.54 cm |
| 2 in | 5.08 cm |
| 5 in | 12.7 cm |
| 10 in | 25.4 cm |
| 20 in | 50.8 cm |
| 50 in | 127 cm |
| 100 in | 254 cm |
| 1,000 in | 2,540 cm |
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How does this tool work?
This converter turns centimeters into inches and inches into centimeters: type a value in either field and the other updates instantly. It covers the everyday cases where metric and US customary units meet: a height given in cm on a European form, a bike frame or a shelf sold in centimeters, clothing measurements from a foreign brand, or a screen size you want to check against the space on your wall.
The inch used here is the international inch (symbol in or ″). Since the 1959 international yard and pound agreement, 1 yard is exactly 0.9144 m, so 1 inch = 1/36 yard = 2.54 cm exactly. It follows that 1 cm ≈ 0.393701 inch.
To go from inches to centimeters, multiply by 2.54; to go from centimeters to inches, divide by 2.54 (or multiply by 0.393701). The inches → cm direction is always exact: 10 inches is exactly 25.4 cm.
For a quick estimate, multiply centimeters by 4 and divide by 10: 50 cm ≈ 20 in (exact value 19.69), about 1.6% high. The other way, multiply inches by 2.5 and add a little: 32 in ≈ 80 cm (exact value 81.28).
Two classic traps: a screen size in inches is the diagonal, not the width (a 55-inch 16:9 TV is about 47.9 in, or 121.8 cm, wide); and a decimal result is not a feet-and-inches value: 70.87 in is 5 ft 10.87 in, never "7.087 ft".
How to use this tool
Enter a measurement
Use the Centimeters field or the Inches field; decimals such as 15.6 are accepted.
Read the result
The other field recalculates on every keystroke, with no button to press.
Swap or scan the chart
The double arrow flips the units; the table below the converter lists common values in both directions.
Cm ↔ inches conversion formulas
The international inch is defined exactly in terms of the meter, so converting inches to centimeters is always exact.
Centimeters to inches
in = cm ÷ 2.54 ≈ cm × 0.393701
The 0.393701 factor is rounded to the millionth.
Width of a 16:9 screen
w = d × 16 ÷ √337 ≈ d × 0.8716
From the Pythagorean theorem: 16² + 9² = 337. The height is d × 9 ÷ √337 ≈ d × 0.4903.
- cm
- length in centimeters
- in
- length in international inches (1 in = 2.54 cm)
- d
- screen diagonal, in any unit
- w
- screen width, in the same unit as d
Example: a 55-inch TV is 55 × 2.54 = 139.7 cm diagonal and about 55 × 0.8716 ≈ 47.9 in (121.8 cm) wide.
Use cases
Screens and monitors
Turn an advertised TV, laptop or tablet diagonal into centimeters, or check a metric spec sheet in inches.
Clothing and body measurements
Convert waist, inseam, chest or height measurements between US/UK sizing and European brands.
Online shopping
Understand the size of furniture, bags or frames sold by European retailers in centimeters.
Crafts and printing
Move between photo sizes (4 × 6 in = 10.16 × 15.24 cm), paper formats and metric patterns.
Examples
Height on a European form
180 ÷ 2.54 ≈ 70.87 in, which is 5 ft 10.87 in (70.87 - 60).
Input
180 cmResult
70.87 inches55-inch TV
55 × 2.54 = 139.7 cm diagonal, about 121.8 cm wide for a 16:9 screen.
Input
55 inchesResult
139.7 cmRoad bike frame
European frame sizes are in cm: 54 ÷ 2.54 ≈ 21.26 in.
Input
54 cmResult
21.26 inchesA4 paper
Slightly narrower and taller than US Letter (8.5 × 11 in).
Input
21 × 29.7 cmResult
8.27 × 11.69 inchesBookshelf width
80 ÷ 2.54 ≈ 31.496 in, handy when checking a flat-pack shelf against a wall gap.
Input
80 cmResult
31.5 inchesTips and best practices
- Quick reference: 1 inch = 2.54 cm and 10 cm ≈ 3.94 inches.
- For a 16:9 screen, the width is about 0.872 times the diagonal and the height about 0.490 times.
- For a height like 5′9″, convert to inches first: 5 × 12 + 9 = 69 in = 175.26 cm.
- For small parts, bolts or wrench sizes, the mm ↔ inches converter is more practical.
- Shoe sizes are not inches: use a dedicated size chart.
Sources and references
- NIST, Guide for the Use of the International System of Units (SP 811), Appendix B.8: Factors for Units Listed Alphabetically (opens in a new tab)Page in English
- BIPM, The International System of Units (SI Brochure) (opens in a new tab), Bureau international des poids et mesuresPage in English
Frequently asked questions
How many centimeters are in an inch?
One inch is exactly 2.54 cm, or 25.4 mm. This value has been fixed since the 1959 international yard and pound agreement.
How do I convert cm to inches?
Divide the centimeters by 2.54, or multiply by 0.393701. For example, 30 cm is about 11.81 inches and 100 cm about 39.37 inches.
What is 180 cm in feet and inches?
180 ÷ 2.54 ≈ 70.87 inches. Divide by 12: 5 feet with 10.87 inches left over, so about 5′11″ rounded.
How big is a 65-inch TV in cm?
65 × 2.54 = 165.1 cm diagonal. For a 16:9 screen that is about 143.9 cm wide and 80.9 cm tall, without bezel or stand.
Why is an inch exactly 2.54 cm?
In 1959 the US, the UK and Commonwealth countries agreed to define the yard as 0.9144 m. Since 1 yard = 36 inches, 1 inch = 0.9144 ÷ 36 = 0.0254 m = 2.54 cm.
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