Jugerum, jugera or jugus (the latter form, as a neuter noun of the third declension, is very common in the oblique cases and in the plural) was a Roman unit of measurement of area, 240 ft or 73 m in length and 120 ft or 37 m in breadth, containing therefore 28,800 square feet (Colum. R. R. v.i § 6; Quintil. i.18). That is 0.65 acre or 0.26 ha.
It was the double of the Actus Quadratus, and from this circumstance, according to some writers, it derived its name (Varro, L. L. v.35, Müller, R. R. i.10). [Actus.] It seems probable that, as the word was evidently originally the same as jugus or jugum, a yoke, and as actus, in its original use, meant a path wide enough to drive a single beast along, that jugerum originally meant a path wide enough for a yoke of oxen, namely, the double of the actus in width; and that when actus quadratos was used for a square measure of surface, the jugerum, by a natural analogy, became the double of the actus quadratus; and that this new meaning of it superseded its old use as the double of the single actus.
Pliny (Book XVIII. Chapter 3) states "That portion of land used to be known as a "jugerum," which was capable of being ploughed by a single "jugum," or yoke of oxen, in one day; an "actus" being as much as the oxen could plough at a single spell, fairly estimated, without stopping. This last was one hundred and twenty feet in length; and two in length made a jugerum." (The Natural History, Pliny the Elder, translated by John Bostock, M.D., F.R.S. H.T. Riley, Esq., B.A. London. Taylor and Francis, Red Lion Court, Fleet Street. 1855).
The uncial division as was applied to the jugerum, its smallest part being the scrupulum of 100 sq ft or 9.2 m². Thus, the jugerum contained 288 scrupula (Varro, R. R. l.c.). The jugerum was the common measure of land among the Romans. Two jugera formed an heredium, a hundred heredia a centuria, and four centuriae a saltus. These divisions were derived from the original assignment of landed property, in which two jugera were given to each citizen as heritable property (Varro, l.c.; Niebuhr, Hist. of Rome, vol. ii pp156, &c., and Appendix ii.).