Kilograms to Roman Pounds (kg to libra)

1 kilogram equals 3.040437823 Roman pounds (rounded).

1 kilogram = 3.040437823 Roman pounds

How to convert kilograms to Roman pounds

To convert kilograms to Roman pounds, multiply the number of kilograms by 3.040437823. The factor is rounded to 10 significant digits. To go the other way, multiply Roman pounds by 0.3289.

Roman pounds = kilograms × 3.040437823

Example: 10 kilograms = 30.40437823 Roman pounds.

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

About these units

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

Roman Pound (libra) (libra)

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

About 328.9 g, divided into 12 unciae. The abbreviation 'lb' for pound comes from libra.

Libra is the Latin word for a balance, and it named both the scales and the standard weight placed on them. It is also known simply as the Roman pound, and the English abbreviation lb is generally traced back to it.

Roman weights counted in twelfths. A libra held 12 unciae, and further fractions such as the scrupulum and the tiny siliqua, about 0.19 g, allowed fine work. The coin called the as shared this scheme: it began as a pound of bronze, then was cut to two ounces after the First Punic War, one ounce during the Second, and half an ounce by the Lex Papiria of 131 BC.

Modern estimates for the libra range from about 322 to 329 g. The figure used here is 328.9 g, about 11.6 oz or 0.725 of an English pound, which is lighter than the avoirdupois pound of 453.6 g. Surviving weights differ among themselves, which is why the exact value stays uncertain.

1 Roman pound (libra) = 0.3289 kilograms (approximately).

Sources: Wikipedia: Roman pound; Wikipedia: Roman units of measurement

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