Ancient Roman units of measurement

thumb|Bronze modius measure (4th century AD) with inscription acknowledging Imperial regulation of weights and measures

The units of measurement of ancient Rome were generally consistent and well documented.

Length

thumb|Roman milestone in modern Austria (AD 201), indicating a distance of 28 Roman miles (~41 km) to [[Teurnia]]

The basic unit of Roman linear measurement was the (plural: ) or Roman foot. 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 of Vespasian previously measured by Villalpandus, a number of brass measuring-rods found in the ruins of Rome, the paving-stones of the Pantheon 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

| palmipes

| foot and a palm

|align="right" | pedes

|align="right" |370 mm 

|align="right" |1.214 ft 

| cubitum

| cubit

|align="right" | pedes

|align="right" |444 mm 

|align="right" |1.456 ft 

| gradus pes sestertius

| step

|align="right" | pedes

|align="right" |0.74 m 

|align="right" |2.427 ft 

| passus

| pace

|align="right" | 5 pedes

|align="right" |1.48 m 

|align="right" |4.854 ft 

| decempeda pertica

| perch

|align="right" | 10 pedes

|align="right" |2.96 m 

|align="right" |9.708 ft 

|path, track

|align="right" | 120 pedes

|align="right" |35.5 m 

|align="right" |116.496 ft 

|24 passus or 12 decembeda

| stadium

| stade

|align="right" | 625 pedes

|align="right" |185 m 

|align="right" |607.14 ft 

| 600 Greek feet or 125 passus or mille

| mille passus mille passuum

| (Roman) mile

|align="right" | 5,000 pedes

|align="right" |1.48 km 

|align="right" |4,854 ft  0.919 mi

| 1000 passus or 8 stadia

| leuga leuca

| (Gallic) league

|align="right" | 7,500 pedes

|align="right" |2.22 km 

|align="right" |7,281 ft  1.379 mi

| colspan=6 style= "font-size:smaller" | Except where noted, based on Smith (1851). and in the name of the Nubian land of Triacontaschoenus between the First and Second Cataracts on the Nile (where it had a value closer to ).

Area

The ordinary units of measurement of area were:

{| class="wikitable" style="margin: 1em auto 1em auto"

|+ Ancient Roman units of area

! Roman unit

! English name

! Equal to

! Metric equivalent

! Imperial equivalent

! Description

| pes quadratus

| square foot

|align="right" | 1 pes qu.

|align="right" | 0.0876 m 

|align="right" | 0.943 sq ft 

| style="max-width:0" | scrupulum or decempeda quadrata

|align="right" | 100 pedes qu.

|align="right" | 8.76 m 

|align="right" | 94.3 sq ft 

| style="max-width:0" | the square of the standard 10-foot measuring rod

| actus simplex

|align="right" | 480 pedes qu.

|align="right" | 42.1 m 

|align="right" | 453 sq ft 

|4 × 120 pedes

| colspan=6 style= "font-size:smaller" | Except where noted, based on Smith (1851).

|style="padding:0 8px; text-align:right;"| 2.84 gal

|style="padding:0 8px; text-align:right;"| 2.94 gal

|colspan=5 style="font-size:smaller;"| Except where noted, based on Smith (1851).

The divisions of the libra were:

{| class="wikitable" style="margin: 1em auto 1em auto"

|+Uncial divisions of the libra

! Roman unit

! English name

! Equal to

! Metric equivalent

! Imperial equivalent

! Description

| uncia

| Roman ounce

|align="right" | libra

|align="right" | 27.4 g 

|align="right" | 0.967 oz 

| "a twelfth"

| sescuncia or sescunx

|align="right" | libra

|align="right" | 41.1 g 

|align="right" | 1.45 oz 

| "one and one-half twelfths"

| sextans

|align="right" | libra

|align="right" | 54.8 g 

|align="right" | 1.93 oz 

| "a sixth"

| quadrans teruncius

|align="right" | libra

|align="right" | 82.2 g 

|align="right" | 2.90 oz 

| "a fourth"  "triple twelfth"

| triens

|align="right" | libra

|align="right" | 109.6 g 

|align="right" | 3.87 oz 

| "a third"

| quincunx

|align="right" | libra

|align="right" | 137.0 g 

|align="right" | 4.83 oz 

| "five-twelfths"

| semis or semissis

|align="right" | libra

|align="right" | 164.5 g 

|align="right" | 5.80 oz 

| "a half"

| septunx

|align="right" | libra

|align="right" | 191.9 g 

|align="right" | 6.77 oz 

| "seven-twelfths"

|bes or bessis

|align="right" | libra

|align="right" | 219.3 g 

|align="right" | 7.74 oz 

| "two [parts] of an as"

| dodrans

|align="right" | libra

|align="right" | 246.7 g 

|align="right" | 8.70 oz 

| "less a fourth"

| dextans

|align="right" | libra

|align="right" | 274.1 g 

|align="right" | 9.67 oz 

| "less a sixth"

| deunx

|align="right" | libra

|align="right" | 301.5 g 

|align="right" | 10.64 oz 

| "less a twelfth"

| libra

| Roman pound libra

| colspan=6 style= "font-size:smaller" | Except where noted, based on Smith (1851).

|align="right" | uncia

|align="right" | 0.57 g 

|align="right" | 8.8 gr  0.020 oz

|  "obol", from the Greek word for "metal spit"

| semisextula or dimidia sextula

|align="right" | uncia

|align="right" | 2.28 g 

|align="right" | 35.2 gr  0.080 oz

|  "half-sixth", "little sixth"

| sextula

| sicilicus or siciliquus

|align="right" | uncia

|align="right" | 6.85 g 

|align="right" | 106 gr  0.242 oz

| "little sickle"

| duella

|align="right" | uncia

|align="right" | 9.14 g 

|align="right" | 141 gr  0.322 oz

|  "little double [sixths]"

| semuncia

| half-ounce semuncia

| uncia

| Roman ounce

|align="right" |

|align="right" | 27.4 g 

|align="right" | 423 gr  0.967 oz

|style="max-width:0" | "a twelfth" In the Julian calendar, an ordinary year is 365 days long, and a leap year 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 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, based on the supposed birth year of Jesus.

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 (i.e. 97 leap years in every 400) to more closely approximate the length of the tropical year.

Weeks

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

Independent of the , astrologers kept a seven-day cycle called a hebdomas 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, Jupiter-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 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 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, thus cementing the seven-day week into Roman civil society.

Hours

The Romans divided the daytime into twelve horae or hours 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 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, 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

Notes

References

</references>

External links

Proposal to Add Ancient Roman Weights and Monetary Signs to UCS (Universal Character Set)

Length

Area

Weeks

Hours

Unicode

See also

Notes

References

External links