Weights and measures were defined by the king. Portugal was feudal and manorial throughout the Middle Ages, but municipalities enjoyed some independence, guaranteed by a Charter, normally issued by the king. This document defined the rights and obligations of the population of each municipality and, naturally, also specified which weights and measures should be used, as they were an important reference for the payment of taxes, which at the time were more often paid in kind than in money.

Reference to measures in the charters predates the establishment of the nationality. The charter granted to Coimbra in 1111 contains the oldest known reference to the alqueire.

The charter that King Afonso Henriques granted to the city of Lisbon in 1179, also makes reference to the alqueire and the almude, among other measures of Arab origin. At the same time, units of Roman origin such as the cúbito and the módio were also used.

This system also included the arrátel, (two pounds), and the arroba, (thirty-two arráteis).