Roman Ounce (uncia) (uncia)

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

One twelfth of a Roman pound, about 27.4 g. The origin of the word 'ounce'.

1 Roman ounce (uncia) = 0.0274 kilograms (approximately).

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

About the Roman ounce (uncia)

Literally meaning a twelfth, uncia was the Roman name for one part in twelve, applied to weight, length and more. As a weight it was a twelfth of a libra. The same word, used for a twelfth of a foot, produced the English inch, so inch and ounce are cousins that split from a single Latin source.

With the libra put at 328.9 g, the uncia comes to about 27.4 g, which is the figure used here. That is a little under the modern avoirdupois ounce of 28.35 g and well below the troy ounce of about 31.1 g. Because the libra itself is estimated anywhere from 322 to 329 g, an uncia could be anywhere from about 26.8 to 27.4 g.

The unit outlived Rome. It continued as the Byzantine ounce, known in Greek as oungia, and in time spread into medieval trade systems across Europe. Many regional ounces developed, such as the Tower ounce and the Dutch ons, which was fixed at 100 g in 1820.

Sources: Wikipedia: Uncia (unit); Wikipedia: Ounce; Wikipedia: Roman pound

Roman Ounce (uncia) conversion chart

1 Roman ounce (uncia) expressed in every other weight & mass unit:

More Ancient Roman units

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• Roman inch (uncia) (length)
• Roman foot (length)
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