Roman Ounces to Kilograms (uncia to kg)

1 Roman ounce (uncia) equals 0.0274 kilograms exactly.

1 Roman ounce (uncia) = 0.0274 kilograms

How to convert Roman ounces to kilograms

To convert Roman ounces to kilograms, multiply the number of Roman ounces by 0.0274. This factor is exact. To go the other way, multiply kilograms by 36.49635036 (rounded).

kilograms = Roman ounces × 0.0274

Example: 10 Roman ounces = 0.274 kilograms.

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 these units

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'.

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.

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

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

Kilogram (kg)

Metric (SI)Current unit

The SI base unit of mass. Since 2019 it is defined by fixing the value of the Planck constant, replacing the old platinum-iridium cylinder in Paris.

Oddly for a base unit, the kilogram began life as a derived one. In 1793 revolutionary France defined the grave as the mass of one litre of water, and a decree of 1795 then replaced it with the kilogramme, a name built from the Greek khilioi (a thousand) and gramma, a Late Latin word for a small weight. In 1799 a platinum cylinder, the Kilogramme des Archives, became the physical standard, matching a cubic decimetre of water at its densest, around 4 degrees Celsius. In 1889 the metric community adopted a platinum-iridium cylinder made in 1879, the International Prototype of the Kilogram, nicknamed Le Grand K.

The kilogram is still the only SI base unit with a prefix in its name. Because SI forbids stacked prefixes, a millionth of a kilogram is a milligram rather than a microkilogram, so every mass prefix is attached to the gram. Calibrating every national standard against one object in a vault near Paris meant that all of them drifted relative to it, so in November 2018 member states voted to tie the kilogram to a fixed value of the Planck constant. The change took effect on 20 May 2019. Day to day nothing shifted, but the definition no longer depends on a single piece of metal.

The kilogram is the reference unit for weight & mass on this site.

Sources: NIST: Kilogram introduction (SI redefinition); Wikipedia: Kilogram

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