jugerum, iugerum

In the Roman Empire, a unit of land area, = 2 actus quadratus = 28,800 square pedes, assuming a pes of around 295 millimeters, roughly a quarter of a hectare or two-thirds of an acre. Hultsch (1862) set it at 2518.88 square meters. In concept, the amount of land that could be plowed by a team of oxen in one day.

The word comes from jugum, yoke, the yoke that harnessed a pair of oxen.

The principal subdivisions of the jugerum were based on the libra/uncia subdivisions, that is, it was divided in twelfths.

Term	Fraction of a jugerum	area in square pedes
jugerum	1	28,800
deunx jugeri	11/12	26,400
dextans jugeri	5/6	24,000
dodrans jugeri	3/4	21,600
bes jugeri	2/3	19,200
septunx jugeriPliny	7/12	16,800
semis jugeri	1/2	14,400
quincunx jugeri	5/12	12,000
triens jugeri	1/3	9,600
quadrans jugeri	1/4	7,200
sextans jugeri	1/6	4,800
uncia jugeri	1/12	2,400
semiuncia jugeri	1/24	1,200
sicilicus jugeri	1/48	600
sextula jugeri	1/72	400
scripulum jugeri	1/288	100

Sources

Iugerum, quod quadratos duos actus habeat. Actus quadratus, qui et latus est pedes CXX et longus totidem: is modus acnua latine appellatur. Iugeri pars minima dicitur scripulum, id est decem pedes et longitudine et latitudine quadratum. Ab hoc principio mensores non numquam dicunt in subsicivum esse unciam agri aut sextantem, sic quid aliud, cum ad iugerum pervenerunt, quod habet iugerum scripula CCLXXXVIII, quantum as antiquos noster ante bellum punicum pendebat.

The iugerum consists of 2 actus quadratus. The actus quadratus, which in width is 120 pedes and the same in length, is called in Latin acnua. The smallest part of a iugerum is called a scripulum; it is a square 10 pedes in length and width. On this principle surveyors sometimes speak of the area beyond the [whole number of] iugerum as an uncia or a sextans, or the like, for the iugerum contains 288 scripula, which was the weight of the old as before the Punic War.

Marcus Varro.
De rustica. Book 1, section 10.

Pliny