Arrobas (Spanish) to Kilograms (@ to kg)

1 arroba (Spanish) equals 11.502325 kilograms exactly.

1 arroba (Spanish) = 11.502325 kilograms

How to convert arrobas (Spanish) to kilograms

To convert arrobas (Spanish) to kilograms, multiply the number of arrobas (Spanish) by 11.502325. This factor is exact. To go the other way, multiply kilograms by 0.08693894495 (rounded).

kilograms = arrobas (Spanish) × 11.502325

Example: 10 arrobas (Spanish) = 115.02325 kilograms.

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

About these units

Arroba (Spanish) (@)

Spanish & PortugueseHistorical unit (no longer in standard use)Approximate value

25 libras, about 11.5 kg. A Castilian weight (and a liquid volume unit); the '@' sign descends from its abbreviation.

Arabic ar-rubʿ, meaning a quarter, is the probable source of arroba, since the unit was the fourth part of a quintal. Moorish rule in Iberia left the word in Spanish and Portuguese, and Wikipedia repeats a tradition, without a source, that it approximated what a donkey could carry. In Castile the quintal was 100 libras, which makes the arroba 25 libras.

With the Castilian libra of 0.460093 kg set in the standard of 1801, the Spanish arroba comes to about 11.5 kg, the figure used here. Similar values were found in Catalonia, Aragon and Andalusia, while the Portuguese arroba was heavier at about 14.7 kg. The same name also applied to a liquid measure for wine and oil, so the word could mean either a weight or a volume depending on the trade.

Colonial administrations took the unit across the Atlantic, where it hardened into different national values: 15 kg in Brazilian cattle and cotton markets, and 12.5 kg in Colombia, Ecuador and Peru. In Spanish and Portuguese the at sign in email addresses is still called arroba, because the symbol was long used as shorthand for the unit.

1 arroba (Spanish) = 11.502325 kilograms (approximately).

Sources: Wikipedia: Arroba; Wikipedia: Spanish customary 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

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