Arroba is a Portuguese and Spanish custom unit of weight, mass or volume. Its symbol is @.
The word arroba has its origin in Arabic ar-rubʿ  (الربع) or "quarter," specifically the fourth part (of a quintal), which defined the average load which a donkey could carry .
In weight it was equal to 32 pounds (14.7 kg) in Portugal and 25 pounds (11.5 kg) in Spain.
The unit is still used in Portugal and Spain by cork merchants and pig farmers.
Arroba and bushel as weight units are similar (15 kg).
The unit is still used in Brazil by the agricultural sector. The modern metric arroba used in these countries in everyday life is defined as 15 kilograms (33 lb).
In Colombia, Ecuador, and Peru the arroba is equivalent to 11.5 kilograms (25 lb).
In Bolivia nationally it is equivalent to 30.46 litres (6.70 imp gal; 8.05 US gal). However locally there are many different values, ranging from 11.5 litres (2.5 imp gal; 3.0 US gal) in Inquisivi to 16 litres (3.5 imp gal; 4.2 US gal) in Baures.
In Spanish-speaking and Portuguese-speaking countries, "arroba" has continued as the word for the "@" symbol used in Internet email addresses.