This page describes an obsolete unit.

The unit described on this page was in use prior to modern methods of precision measurement. It was based on a standard which is no longer available, and which is not capable of being calibrated against modern measurement units. Therefore, the equivalence to modern SI units or to current United States customary units can only be considered approximate.

The libra (often translated as pound) was a pre-metric unit of mass or weight in Spain, and was carried to the Spanish colonies and used there.

The standard value of the libra was considered to be the libra of Avila or Castilla, at 460 g (1.01 lb); however, a number of other values[1] were used in the various provinces of Spain:

Libra of Value
Avila or Castilla 460 g (1.014 lb)
Baleares 407 g (0.897 lb)
Caceres 456 g (1.005 lb)
Castellón 358 g (0.789 lb)
Coruña 575 g (1.268 lb)
Gerona 400 g (0.882 lb)
Guipizcoa 492 g (1.085 lb)
Huesca 351 g (0.774 lb)
Lérida 400 g (0.882 lb)
Lugo 533 g (1.175 lb)
Navarra 372 g (0.82 lb)
Pontevedra 574 g (1.265 lb)
Tarragona 579 g (1.276 lb)
Teruel 367 g (0.809 lb)
Valencia 355 g (0.783 lb)
Vizcaya 488 g (1.076 lb)
Zaragoza 350 g (0.772 lb)

In Aragón, Baleares, Catalonia, and Valencia, the libra was divided into 12 onzas (usually rendered as ounces), while in the Basque provinces it was divided into 17, and in Galicia, into 20.[1]


  1. 1.0 1.1 Naft, Stephen (1961). Ralph DeSola. ed. International Conversion Tables. New York, N. Y.: Duell, Sloan and Pearce. p. 33. 

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