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The ancient Roman units of measurement were primarily founded on the Hellenic system, which in turn was influenced by the Egyptian system and the Mesopotamian system. The
Roman Roman or Romans most often refers to: * Rome, the capital city of Italy * Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a lett ...
units were comparatively consistent and well documented.


Length

The basic unit of Roman linear measurement was the ''pes'' or Roman foot (plural: ''pedes''). Investigation of its relation to the English foot goes back at least to 1647, when John Greaves published his ''Discourse on the Romane foot''. Greaves visited Rome in 1639, and measured, among other things, the foot measure on the tomb of Titus Statilius Aper, that on the statue of Cossutius formerly in the gardens of Angelo Colocci, the
congius In Ancient Roman measurement, ''congius'' (pl. ''congii'', from Greek ''konkhion'', diminutive of ''konkhē'', ''konkhos'', "shellful") was a liquid measure that was about 3.48 litres (0.92 U.S. gallons). It was equal to the larger chous of the A ...
of Vespasian previously measured by Villalpandus, a number of brass measuring-rods found in the ruins of Rome, the paving-stones of the
Pantheon Pantheon may refer to: * Pantheon (religion), a set of gods belonging to a particular religion or tradition, and a temple or sacred building Arts and entertainment Comics *Pantheon (Marvel Comics), a fictional organization * ''Pantheon'' (Lone St ...
and many other ancient Roman buildings, and the distance between the milestones on the Appian Way. He concluded that the Cossutian foot was the "true" Roman foot, and reported these values compared to the iron standard of the English foot in the Guildhall in London (30.4919cm):
Smith Smith may refer to: People * Metalsmith, or simply smith, a craftsman fashioning tools or works of art out of various metals * Smith (given name) * Smith (surname), a family name originating in England, Scotland and Ireland ** List of people wit ...
(1851) gives a value of 0.9708 English feet, or about 295.9 mm. An accepted modern value is 296 mm. The Roman foot was sub-divided either like the Greek ''pous'' into 16 ''digiti'' or fingers; or into 12 ''unciae'' or inches.
Frontinus Sextus Julius Frontinus (c. 40 – 103 AD) was a prominent Roman civil engineer, author, soldier and senator of the late 1st century AD. He was a successful general under Domitian, commanding forces in Roman Britain, and on the Rhine and Danube ...
writes in the 1st century AD that the ''digitus'' was used in
Campania (man), it, Campana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = , demographics1_footnotes = , demographics1_title1 = , demographics1_info1 = , demog ...
and most parts of Italy. The principal Roman units of length were: Other units include the
schoenus Schoenus ( la, schœnus; grc-gre, σχοίνος, ''schoinos'',  " rush rope"; egy, i͗trw, "river-measure") was an ancient Egyptian, Greek and Roman unit of length and area based on the knotted cords first used in Egyptian surveying. ...
(from the Greek for " rush rope") used for the distances in Isidore of Charax's ''
Parthian Stations Isidore of Charax (; grc, Ἰσίδωρος ὁ Χαρακηνός, ''Isídōros o Charakēnós''; la, Isidorus Characenus) was a Greco-Roman geographer of the 1st century BC and 1st century AD, a citizen of the Parthian Empire, about whom nothi ...
'' (where it had a value around ) and in the name of the Nubian land of
Triacontaschoenus The Triakontaschoinos ( el, Τριακοντάσχοινος, "Land of the Thirty '' Schoinoi''"), Latinized as Triacontaschoenus, was a geographical and administrative term used in the Greco-Roman world for the part of Lower Nubia between the Fir ...
between the First and
Second Cataract The Cataracts of the Nile are shallow lengths (or whitewater rapids) of the Nile river, between Khartoum and Aswan, where the surface of the water is broken by many small boulders and stones jutting out of the river bed, as well as many rocky ...
s on the
Nile The Nile, , Bohairic , lg, Kiira , Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered the longest ri ...
(where it had a value closer to ).


Area

The ordinary units of measurement of area were: Other units of area described by
Columella Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the wo ...
in his ''De Re Rustica'' include the ''porca'' of 180 × 30 Roman feet (about ) used in
Hispania Baetica Hispania Baetica, often abbreviated Baetica, was one of three Roman provinces in Hispania (the Iberian Peninsula). Baetica was bordered to the west by Lusitania, and to the northeast by Hispania Tarraconensis. Baetica remained one of the basic di ...
and the Gallic ''candetum'' or ''cadetum'' of 100 feet in the city or 150 in the country. Columella also gives uncial divisions of the ''jugerum'', tabulated by the anonymous translator of the 1745 Millar edition as follows:


Volume

Both liquid and dry volume measurements were based on the sextarius. The sextarius was defined as of a cubic foot, known as an amphora quadrantal. Using the value for the Roman foot, an amphora quadrantal can be computed at approximately , so a sextarius (by the same method) would theoretically measure , which is about 95% of an imperial pint (568.26125 ml). Archaeologically, however, the evidence is not as precise. No two surviving vessels measure an identical volume, and scholarly opinion on the actual volume ranges between and . The core volume units are: * '' amphora quadrantal'' (Roman jar) – one cubic ''pes'' (Roman foot) * ''congius'' – a half-''pes'' cube (thus ''amphora quadrantal'') * ''sextarius'' – literally of a ''congius''


Liquid measure


Dry measure


Weight

The units of weight or mass were mostly based on factors of 12. Several of the unit names were also the names of coins during the Roman Republic and had the same fractional value of a larger base unit: libra for weight and as for coin. Modern estimates of the libra range from with 5076 grains or an accepted figure. The ''as'' was reduced from 12 ounces to 2 after the First Punic War, to 1 during the Second Punic War, and to half an ounce by the 131 BC
Lex Papiria The ballot laws of the Roman Republic (Latin: ''leges tabellariae'') were four laws which introduced the secret ballot to all popular assemblies in the Republic.Yakobson (1995), p. 426. They were all introduced by tribunes, and consisted of t ...
... The divisions of the libra were: The subdivisions of the uncia were:


Time


Years

The complicated Roman calendar was replaced by the Julian calendar in 45 BC. In the Julian calendar, an ordinary year is 365 days long, and a
leap year A leap year (also known as an intercalary year or bissextile year) is a calendar year that contains an additional day (or, in the case of a lunisolar calendar, a month) added to keep the calendar year synchronized with the astronomical year o ...
is 366 days long. Between 45 BC and AD 1, leap years occurred at irregular intervals. Starting in AD 4, leap years occurred regularly every four years. Year numbers were rarely used; rather, the year was specified by naming the Roman consuls for that year. (As consuls' terms latterly ran from January to December, this eventually caused January, rather than March, to be considered the start of the year.) When a year number was required, the Greek
Olympiads An olympiad ( el, Ὀλυμπιάς, ''Olympiás'') is a period of four years, particularly those associated with the ancient and modern Olympic Games. Although the ancient Olympics were established during Greece's Archaic Era, it was not until ...
were used, or the count of years since the founding of Rome, "
ab urbe condita ''Ab urbe condita'' ( 'from the founding of the City'), or ''anno urbis conditae'' (; 'in the year since the city's founding'), abbreviated as AUC or AVC, expresses a date in years since 753 BC, the traditional founding of Rome. It is an ex ...
" in 753 BC. In the Middle Ages, the year numbering was changed to the
Anno Domini The terms (AD) and before Christ (BC) are used to label or number years in the Julian and Gregorian calendars. The term is Medieval Latin and means 'in the year of the Lord', but is often presented using "our Lord" instead of "the Lord", ...
count. The calendar used in most of the modern world, the Gregorian calendar, differs from the Julian calendar in that it skips three leap years every four centuries to more closely approximate the length of the
tropical year A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky of a celestial body of the Solar System such as the Earth, completing a full cycle of seasons; for example, the time fro ...
.


Weeks

The Romans grouped days into an eight-day cycle called the , with every eighth day being a market day. Independent of the ,
astrologer Astrology is a range of divinatory practices, recognized as pseudoscientific since the 18th century, that claim to discern information about human affairs and terrestrial events by studying the apparent positions of celestial objects. Dif ...
s kept a seven-day cycle called a '' hebdomas'' where each day corresponded to one of the seven
classical planets In classical antiquity, the seven classical planets or seven luminaries are the seven moving astronomical objects in the sky visible to the naked eye: the Moon, Mercury, Venus, the Sun, Mars, Jupiter, and Saturn. The word ''planet'' comes from ...
, with the first day of the week being Saturn-day, followed by Sun-day, Moon-day, Mars-day, Mercury-day, Jupiter-day, and lastly Venus-day. Each astrological day was reckoned to begin at sunrise. The
Jew Jews ( he, יְהוּדִים, , ) or Jewish people are an ethnoreligious group and nation originating from the Israelites Israelite origins and kingdom: "The first act in the long drama of Jewish history is the age of the Israelites""The ...
s also use a seven-day week, which began Saturday evening. The seventh day of the week they called Sabbath; the other days they numbered rather than named, except for Friday, which could be called either the Parasceve or the sixth day. Each Jewish day begins at sunset.
Christians Christians () are people who follow or adhere to Christianity, a monotheistic Abrahamic religion based on the life and teachings of Jesus Christ. The words ''Christ'' and ''Christian'' derive from the Koine Greek title ''Christós'' (Χρι� ...
followed the Jewish seven-day week, except that they commonly called the first day of the week the , or the Lord's day. In 321, Constantine the Great gave his subjects every Sunday off in honor of his family's tutelary deity, the Unconquered Sun, thus cementing the seven-day week into Roman civil society.


Hours

The Romans divided the daytime into twelve ''horae'' or
hour An hour (symbol: h; also abbreviated hr) is a unit of time conventionally reckoned as of a day and scientifically reckoned between 3,599 and 3,601 seconds, depending on the speed of Earth's rotation. There are 60 minutes in an hour, and 24 hou ...
s starting at sunrise and ending at sunset. The night was divided into four watches. The duration of these hours varied with seasons; in the winter, when the daylight period was shorter, its 12 hours were correspondingly shorter and its four watches were correspondingly longer. Astrologers divided the
solar day A synodic day (or synodic rotation period or solar day) is the period for a celestial object to rotate once in relation to the star it is orbiting, and is the basis of solar time. The synodic day is distinguished from the sidereal day, which is ...
into 24 equal hours, and these astrological hours became the basis for medieval
clock A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and the ...
s and our modern 24-hour mean solar day. Although the division of hours into minutes and seconds did not occur until the Middle Ages, Classical astrologers had a ''minuta'' equal to of a day (24 modern minutes), a ''secunda'' equal to of a day (24 modern seconds), and a ''tertia'' equal to of a day (0.4 modern seconds).


Unicode

A number of special symbols for Roman currency were added to the Unicode Standard version 5.1 (April 2008) as the Ancient Symbols block (U+10190–U+101CF, in the Supplementary Multilingual Plane ). As mentioned above, the names for divisions of an coin (originally one libra of bronze) were also used for divisions of a libra, and the symbols U+10190–U+10195 are likewise also symbols for weights: * U+10190 (𐆐): Sextans * U+10191 (𐆑): Uncia * U+10192 (𐆒): Semuncia * U+10193 (𐆓): Sextula * U+10194 (𐆔): Semisextula * U+10195 (𐆕): Siliqua


See also

* Ancient Egyptian units *
Ancient Greek units Ancient history is a time period from the beginning of writing and recorded human history to as far as late antiquity. The span of recorded history is roughly 5,000 years, beginning with the Sumerian cuneiform script. Ancient history cove ...
*
Biblical and Talmudic units of measurement Biblical and Talmudic units of measurement were used primarily by ancient Israelites and appear frequently within the Hebrew Bible as well as in later rabbinic writings, such as the Mishnah and Talmud. These units of measurement continue to be used ...
*
Byzantine units Byzantine units of measurement were a combination and modification of the ancient Greek and Roman units of measurement used in the Byzantine Empire. Until the reign of Justinian I (527–565), no universal system of units of measurement existed ...
* History of measurement


References


External links


Proposal to Add Ancient Roman Weights and Monetary Signs to UCS (Universal Character Set)
{{Systems of measurement