Centimeters to Millimeters (cm to mm)

1 centimeter equals 10 millimeters exactly.

1 centimeter = 10 millimeters

How to convert centimeters to millimeters

To convert centimeters to millimeters, multiply the number of centimeters by 10. This factor is exact. To go the other way, multiply millimeters by 0.1.

millimeters = centimeters × 10

Example: 10 centimeters = 100 millimeters.

About these units

Centimeter (cm)

Metric (SI)Current unit

One hundredth of a meter. Used for body measurements, clothing and everyday objects.

Scientists, rather than shopkeepers, gave the centimeter its place. In 1832 Carl Friedrich Gauss proposed a system of absolute units built on length, mass and time, choosing the millimeter, milligram and second. In 1873 a committee of the British Association for the Advancement of Science, whose members included James Clerk Maxwell and William Thomson (Lord Kelvin), recommended the centimeter, gram and second instead. That CGS system dominated physics for decades, until the metre-kilogram-second system replaced it in the mid-twentieth century and led to SI.

CGS units proved awkward for rooms and buildings, which run to hundreds of centimeters, but the centimeter itself never went away. It is still the everyday unit for height, clothing and small objects, and it appears in map scales and rainfall reports. An adult fingernail is roughly one centimeter wide, and a milliliter is defined as exactly one cubic centimeter. An inch is exactly 2.54 centimeters. The CGS system itself survives mainly in theoretical physics and astrophysics, where Gaussian units are still common.

1 centimeter = 0.01 meters (exactly).

Sources: Wikipedia: Centimetre-gram-second system of units; Wikipedia: Centimetre; NIST Guide to the SI, Appendix B.8: conversion factors

Millimeter (mm)

Metric (SI)Current unit

One thousandth of a meter. Used in engineering, manufacturing and rainfall measurement.

Carl Friedrich Gauss put the millimeter at the base of his 1832 proposal for absolute units, pairing it with the milligram and the second, although the centimeter-based CGS system later won out among scientists. The name combines the metric prefix milli-, from the Latin for one thousand, with the meter. Since 1983 a millimeter has been tied to the speed of light: it is the distance light covers in 1/299,792,458,000 of a second.

Millimeters are the language of fine mechanical work. Standard rulers are divided into them, digital calipers commonly read to 0.01 mm, and mechanical pencil leads come in 0.5 and 0.7 mm. Copy paper is about 0.1 mm thick, and a thin hair, at 0.02 to 0.04 mm across, is close to the smallest thing the naked eye can see. A wave with a frequency of 300 GHz has a wavelength of 1 mm. An inch is exactly 25.4 mm. One trap for readers in the United States is that mil there traditionally means a thousandth of an inch, not a millimeter.

1 millimeter = 0.001 meters (exactly).

Sources: Wikipedia: Millimetre; Wikipedia: Centimetre-gram-second system of units; NIST Guide to the SI, Appendix B.8: conversion factors

Related conversions

See all length units.