One thousandth of an inch, 0.00254 cm, used for film and coating thickness. It is not a millimetre, and confusing the two is a factor-of-forty mistake.

Converters Length

Inches to centimetres

Inches

Centimetres 2.54

Decimals

Live · 1 in = 2.54 cm exactly

Inches, including screen sizes

1 in 2.54 cm

6 in 15.24 cm

12 in 30.48 cm

24 in 60.96 cm

32 in 81.28 cm

55 in 139.7 cm

65 in 165.1 cm

Multiply inches by 2.54 to get centimetres. The factor is exact by definition, not a measurement. A 55-inch television is 139.7 cm on the diagonal, a 12-inch ruler is 30.48 cm, and a sheet of US Letter paper at 8.5 by 11 inches is 21.59 by 27.94 cm.

How to convert inches to centimetres

1 Enter the length in inches. Decimals are fine; type 5.75 for five and three-quarters.

2 Read the centimetre figure below.

3 Press ⇄ to convert centimetres back to inches.

Nominal sizes are the trap. A "two by four" is not two inches by four — it is planed down to 1.5 by 3.5 inches, so 3.81 by 8.89 cm. Pipe and screw sizes carry the same kind of legacy naming, where the label stopped describing the measurement a century ago.

Questions

How do I enter a fraction? −

Convert it to a decimal first: a half is 0.5, a quarter 0.25, an eighth 0.125 and a sixteenth 0.0625. So 3⅜ inches is 3.375.

How big is a 55-inch TV really? +

Is A4 the same as US Letter? +

What is a mil? +

Sources

NIST — the United States and the metric system ISO 216 — writing paper and certain classes of printed matter

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