Arrobas (Spanish) to Pounds (@ to lb)
1 arroba (Spanish) equals 25.3582859 pounds (rounded).
How to convert arrobas (Spanish) to pounds
To convert arrobas (Spanish) to pounds, multiply the number of arrobas (Spanish) by 25.3582859. The factor is rounded to 10 significant digits. To go the other way, multiply pounds by 0.03943484209 (rounded).
pounds = arrobas (Spanish) × 25.3582859
Example: 10 arrobas (Spanish) = 253.582859 pounds.
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) (@)
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
Pound (lb)
Exactly 0.45359237 kg, divided into 16 ounces. The standard unit of weight in the US and common in the UK.
Why is pound abbreviated lb? The answer is Roman. The English word comes from the Latin libra pondo, roughly the weight measured in libra, and the symbol keeps the first word. The Roman libra was divided into 12 unciae. The avoirdupois pound of 16 ounces came into general use around 1300 and was initially equal to 6,992 troy grains; under Elizabeth I it was redefined as 7,000 grains. The UK's Weights and Measures Act 1878 set the imperial standard pound as a platinum cylinder, and the troy pound was abolished for trade the following year.
Today the pound is defined from the kilogram. The International Yard and Pound Agreement of 1959 fixed it at exactly 0.45359237 kg, and the UK's Weights and Measures Act 1963 wrote the same figure into law. Pounds remain the everyday unit for body weight, groceries and shipping in the United States and are widely used in the UK. The word also survives in odd places: a six-pounder cannon was named for the weight of its shot, not its own.
1 pound = 0.45359237 kilograms (exactly).
Sources: Wikipedia: Pound (mass); NIST Guide to the SI, Appendix B.8 (mass conversions)
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