uncia

ancient unit of length

Also known as: inch, pollicus

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Last updated

June 17, 2026

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The uncia was an ancient Roman unit of measurement, primarily used for length and weight. As a unit of length, it represented the 12th part of a Roman foot, which is equivalent to the modern inch. The Roman foot itself was divided into 16 digits or 12 unciae, with the uncia measuring approximately 24.67 mm or 0.97 inches.123

In terms of weight, the uncia also denoted the 12th part of a Roman pound. This system influenced the development of units in Old English and modern English, leading to terms like "inch" and "ounce". The Roman pound was divided into 12 unciae, and in the troy system, the ounce also represented the 12th part of a pound.1

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measurement system
Greeks and Romans
73 inch); the inch (uncia or pollicus), or 1/12 Roman foot, was 24.67 mm (0.97 inch); and the palm (palmus), or 1/4 Roman foot, was 74 mm (2.91 inches).
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73 inch); the inch (uncia or pollicus), or 1/12 Roman foot, was 24.67 mm (0.97 inch); and the palm (palmus), or 1/4 Roman foot, was 74 mm (2.91 inches).
Read More