Ancient Roman units of measurement


Ancient Roman units of measurement

The ancient Roman units of measurement were built on the Hellenic system with Egyptian, Hebrew, and Mesopotamian influences. The Roman units were comparatively consistent and well documented.

Contents

Length

Roman unit Latin name Feet Equivalence
one digit digitus 116 18.5 mm
one inch uncia 112 24.6 mm
one palm palmus 14 74 mm
one foot pes 1 29.6 cm[1]
one cubit cubitus 1 12 44.4 cm
one step gradus 2 12 0.74 m
one pace passus 5 1.48 m
one fathom ulna 6 1.78 m
one perch pertica 10 2.96 m
one arpent actus 120 35.5 m
one furlong stadium 625 185 m
one mile mille passuum (milliarium) 5000 1.48 km
one league leuga 7500 2.2225 km

Notes

  1. From late Antiquity the Roman foot was sometimes divided into unciae comprising 12 equal parts.
    The ancient digit measure, however, largely dominated before the beginning of the Middle Ages.[citation needed]
  2. A Roman foot was approximately equal to the height of a modern A4 sheet of paper.

Area

Roman unit Latin name Acres Equivalence
one square foot pes quadratus 114 400 ~ 876 cm²
one square perch scripulum 1144 ~ 8.76 m²
one aune of furrows actus minimus 130 ~ 42 m²
one rood clima 14 ~ 315 m²
one acre actus quadratus
also known as acnua
1 ~ 1260 m²
one yoke iugerum 2 ~ 2520 m²
one morn heredium 4 ~ 5040 m²
one centurie centuria 400 ~ 50.5 ha
one "quadruplex" saltus 1600 ~ 201.9 ha

The Roman acre is the squared Roman arpent, 120 pedes by 120 pedes. This equals 14 400 square feet or about 0.126 hectares.

The Romans also had a unit of area called a quinaria, which was used to measure the cross-sectional area of pipes. One quinaria was considered to be roughly 4.2 cm².

Note:  Some researchers assert that the Roman surveyors used a perch of ten Greek "Pous of Kyrenaika", i.e. 3.087 m instead of the perch of ten of their own feet, equal 2.964 m.
According to this hypothesis  – currently not supported by the majority of modern metrologists –; all the Roman area measures should be multiplied by 625/576, i.e. 8.5 % larger.
If the irrefutable proof for the real existence of a Roman surveyor perch of 10 Roman feet  6⅔ digits can be adduced, then the saltus equates to one Roman square mile exactly.

Volume

Liquid measures

Roman unit Latin name Sesters Equivalence
one spoonful ligula 148 ~ 11.25 ml
one dose cyathus 112 ~ 45 ml
one sixth-sester sextans 16 ~ 90 ml
one third-sester triens 13 ~ 180 ml
one half-sester hemina 12 ~ 270 ml
one double third-sester choenix 23 ~ 360 ml
one sester sextarius 1 ~ 540 ml
one congius congius 6 ~ 3.25 l
one urn urna 24 ~ 13 l
one jar amphora 48 ~ 26 l
one hose culleus 960 ~ 520 l

The Roman jar, so-called "amphora quadrantal" is the cubic foot. The congius is half-a-foot cubed. The Roman sester is the sixth of a congius.

Dry measures

Bronze modius (4th cent. CE)
Roman unit Latin name Pecks Equivalence
one drawing-spoon acetabulum 1128 ~ 67.5 ml
one quarter-sester quartarius 164 ~ 135 ml
one half-sester hemina 132 ~ 270 ml
one sester sextarius 116 ~ 540 ml
one gallon semodius 12 ~ 4 13 l
one peck modius 1 ~ 8 23 l
one bushel quadrantal 3 ~ 26 l

Like the jar, the Roman bushel or "quadrantal" is one cubic foot. It is almost 26.027 litres. One-third of a quandrantal is a Roman peck.

Mass

The units of weight (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 mass and as for coin. The modern mass of the libra is estimated to range from 322 to 327 grams (11.4 to 11.5 oz).[2]

Unit of mass Conversion
Centum podium &10000000000001200000000 100 libra
Mina &1000000000000002000000020 uncia
Libra (podium) &1000000000000001200000012 uncia
Deunx &1000000000000001100000011 uncia
Dextans &1000000000000001000000010 uncia
Dodrans &100000000000000090000009 uncia
Bes &100000000000000080000008 uncia
Septunx &100000000000000070000007 uncia
Semis &100000000000000060000006 uncia
Quincunx &100000000000000050000005 uncia
Triens &100000000000000040000004 uncia
Quadrans &100000000000000030000003 uncia
Sextans &100000000000000020000002 uncia
Uncia (ounce) &10000000000000001000000
Semuncia &1000000000000000050000012 uncia
Duella &1000000000000000033000013 uncia
Sicilium &1000000000000000025000014 uncia
Miliaresium &1000000000000000020000015 uncia
Solidus (sextula) &1000000000000000017000016 uncia
Denarius &1000000000000000014000017 uncia
Denier &1000000000000000012500018 uncia
Scripulum &1000000000000000004000013 denier

Reference: Cardarelli, François (2003). Encyclopaedia of Scientific Units, Weights and Measures: Their SI Equivalences and Origins. Trans. M.J. Shields. London: Springer-Verlag. pp. 74–5. ISBN 978-1-85233-682-X. http://books.google.com/books?id=GV1aV7V7I00C&pg=SA3-PA72. Retrieved 18 November 2011. 

One and a half ounces was called by Romans "sescuncia". The Roman pound is exactly three quarters of the Greek mine. Thus the Greek and Roman drachm is related by the ratio 32 to 25.[citation needed]

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, a leap year is 366 days long. Between 45 BC and 1 AD, leap years occurred at irregular intervals. Starting in the year 4 AD, 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. When a year number was required, the Greek Olympiads were used, or the count of years since the founding of Rome, "Ab urbe condita" in 753 BC. In the middle ages, the year numbering was changed to the Anno Domini count.

Our currently used 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.

Weeks

The Romans grouped days into an eight-day cycle called a nundina, with every eighth day being a market day.

Independent of the nundinae, astrologers kept a seven-day cycle called a hebdomada where each day corresponded to one of the seven classical planets, with the first day of the week being Saturn-day, followed by Sun-day, Moon-day, Mars-day, Mercury-day, Jove-day, and lastly Venus-day. Each astrological day was reckoned to begin at sunrise. The Jews also used a seven-day week, which began Saturday evening. The seventh day of the week they called the 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 was reckoned to begin at sunset. Christians followed the Jewish seven-day week, except that they commonly called the first day of the week the Dominica, 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 hours starting in the morning and ending in the evening. 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 into 24 equal hours, and these astrological hours became the basis for medieval clocks and our modern 24 hour mean solar day.

Although the division of hours into minutes and seconds did not occur until the middle ages, ancient astrologers had a minuta equal to a 60th of a day, and a secunda equal to one 3600th of a day.

See also

References

  1. ^ Hosch, William L. (ed.) (2010) The Britannica Guide to Numbers and Measurement New York, NY: Britannica Educational Publications, 1st edition. ISBN 9781615301089, p.206
  2. ^ Laniado, Avshalom; Dashti, Batya (1993). "A Byzantine lead weight from the port of Iamnia (Yavneh-Yam) and the title 'ΈΦΟΡΟΣ". Revue des études byzantines (Paris) 51 (51): 229–35. ISSN 0766-5598. http://www.persee.fr/web/revues/home/prescript/article/rebyz_0766-5598_1993_num_51_1_1879. Retrieved 19 November 2011. 

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