Centimeters to Roman Inches (cm to uncia)

1 centimeter equals 0.406504065 Roman inches (rounded).

1 centimeter = 0.406504065 Roman inches

How to convert centimeters to Roman inches

To convert centimeters to Roman inches, multiply the number of centimeters by 0.406504065. The factor is rounded to 10 significant digits. To go the other way, multiply Roman inches by 2.46.

Roman inches = centimeters × 0.406504065

Example: 10 centimeters = 4.06504065 Roman inches.

Approximate value. Standards for the Roman inch (uncia) varied by place and period, so this converter uses the most commonly cited value. Treat results as estimates, not exact figures.

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

Roman Inch (uncia) (uncia)

Ancient RomanHistorical unit (no longer in standard use)Approximate value

One twelfth of a Roman foot, about 2.46 cm. Its name, uncia, is the root of the English words 'inch' and 'ounce'.

Twelve of these made up a Roman foot, and that fraction is the whole meaning of the name: uncia is Latin for a twelfth. The same word was applied to weight, where it gave the ounce as a twelfth of the Roman pound. Because the foot is about 296 mm, the uncia works out to roughly 24.6 mm, the value Wikipedia gives, though that article notes the figure lacks a citation. Any difference in the foot carries straight through to its inch.

Latin also had pollex, meaning thumb, as a synonym for the length. Old English borrowed uncia as ynce, and a regular sound change turned it into the modern word inch, which is a cousin of ounce. The English inch kept the idea of a twelfth of a foot but was later fixed by international agreement at exactly 25.4 mm, so it is about 3 percent larger than the Roman original.

1 Roman inch (uncia) = 0.0246 meters (approximately).

Sources: Wikipedia: Roman inch; Wikipedia: Inch; Wikipedia: Ancient Roman units of measurement

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