From Wikipedia, the free encyclopedia
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.
Length
Modern metrologists have found the Roman foot to
be ^{16}⁄_{28}
of the Nippur cubit.
Roman unit 
Latin name 
Feet 
Equivalence 
one digit 
digitus 
^{1}⁄_{16} 
18.5 mm 
one inch 
uncia 
^{1}⁄_{12} 
24.6 mm 
one palm 
palmus 
^{1}⁄_{4} 
74 mm 
one foot 
pes 
1 
296 mm^{[1]} 
one cubit 
cubitus 
1+^{1}⁄_{2} 
444 mm 
one step 
gradus 
2+^{1}⁄_{2} 
0.74 m 
one pace 
passus 
5 
1.48 m 
one perch 
pertica 
10 
2.96 m 
one arpent 
actus 
120 
35.5 m 
one stadium 
stadium 
625 
185 m 
one mile 
mille passuum (milliarium) 
5000 
1.48 km 
one league 
leuga 
7500 
2.22 km 
Notes
 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.
 The value of the historical Roman foot scientifically obtained
through modern statistical methods is
296.2 mm ± 0.5 mm, or about
(296.2 ± 0.17%) mm (cf. Rottländer, Tübingen,
Germany). The table above is based on this value, but rounded
to the millimetre precision for the foot.
 The widely accepted ratio between the Roman foot and the
English foot is 36:35. That is, 36 Roman feet to 35 English feet,
making the Roman foot slightly shorter than its modern equivalent.
The latter one is 16/28 Mesopotamian
cubit and the ratio between this one and the Roman cubit is
20:24. If the present English foot is taken as for reference, the
Roman foot should be 296 1/3 mm or approximately 11.65
English inches. That is within the margin obtained by
R.C.A. Rottländer (see references).
 A Roman foot can be visualised as being approximately equal to
the height of an A4 sheet of
paper (297 mm). This comparison, although descriptive, is
+0.27% out of the range given above.
Area
Roman unit 
Latin name 
Acres 
Equivalence 
one square foot

pes quadratus

^{1}⁄_{14
400}

~ 876 cm²

one square perch

scripulum

^{1}⁄_{144}

~ 8.76 m²

one aune of furrows

actus minimus

^{1}⁄_{30}

~ 42 m²

one rood

clima

^{1}⁄_{4}

~ 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

centurium

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
crosssectional 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

^{1}⁄_{48}

~ 1+^{1}⁄_{8}
cl

one dose

cyathus

^{1}⁄_{12}

~ 4+^{1}⁄_{2}
cl

one sixthsester

sextans

^{1}⁄_{6}

~ 9 cl

one thirdsester

triens

^{1}⁄_{3}

~ 18 cl

one halfsester

hemina

^{1}⁄_{2}

~ 27 cl

one double thirdsester

choenix

^{2}⁄_{3}

~ 36 cl

one sester

sextarius

1

~ 54 cl

one congius

congius

6

~ 3+^{1}⁄_{4}
l

one urn

urna

24

~ 13 l

one jar

amphora

48

~ 26 l

one hose

culleus

960

~ 520 l

The Roman jar, socalled "amphora
quadrantal" is the cubic foot. The congius is halfafoot
cubed. The Roman sester is the sixth of a congius.
Dry
measures
Bronze
modius (4th cent. CE)
Roman unit 
Latin name 
Pecks 
Equivalence 
one drawingspoon

acetabulum

^{1}⁄_{128}

~ 6+^{3}⁄_{4}
cl

one quartersester

quartarius

^{1}⁄_{64}

~ 13+^{1}⁄_{2}
cl

one halfsester

hemina

^{1}⁄_{32}

~ 27 cl

one sester

sextarius

^{1}⁄_{16}

~ 54 cl

one gallon

semodius

^{1}⁄_{2}

~ 4+^{1}⁄_{3}
l

one peck

modius

1

~ 8+^{2}⁄_{3}
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. Onethird of a quandrantal is a
Roman peck.
Mass and
coins
Roman unit

Latin name

Drachms

Equivalence

one chalcus

chalcus

1 / 48

~ 71 mg

one siliqua

siliqua

1 / 18

~ 189⅓ mg

one obolus

obolus

1 / 6

~ 0.568 g

one scruple

scrupulum

1 / 3

~ 1.136 g

one dram

drachma

1

~ 3.408 g

one shekel

sicilicus

2

~ 6.816 g

one ounce

uncia

8

~ 27.264 g

one pound

libra

96

~ 327.168 g

one mine

mina

128

~ 436.224 g

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.
All the multiples of
the Roman ounce have their own names 
1 ounce =

uncia

7 ounces =

septunx

2 ounces =

semis

8 ounces =

bes

3 ounces =

triens

9 ounces =

dodrans

4 ounces =

quadrans

10 ounces =

dextans

5 ounces =

quincunx

11 ounces =

deunx

6 ounces =

sextans

12 ounces =

as

One and a half ounces was called by Romans "sescuncia". Some of
these nouns were used to designate Roman bronze coins.
Time
The Julian
calendar was introduced in 45 BC replacing the earlier Roman calendar.
In the Julian calendar, an ordinary year is 365 days long, a leap
year is 366 days long, and every fourth year is a leap year. 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.
References
 ^
Accuracy of length units
Google translation of http://vormetrischelaengeneinheiten.de/html/genauigkeit.html
by Rolf C. A. Rottländer, Rottenburg / Köln
Sources
 Vormetrische
Längeneinheiten by Rolf C. A. Rottländer,
Rottenburg / Köln (also see SearchEngine).
 Recovery of the Ancient
System Foot/Cubit/Stadion by Dieter Lelgemann, acting
Director of the Institute for Geodesy and GeoInformation
Technology, TU Berlin.
 On the Ancient Determination
of Meridian Arc Length by Eratosthenes of Kyrene Dieter
Lelgemann, WS – History of Surveying and Measurement, Athens,
Greece, May 2227, 2004.
 Knobloch, Eberhard,
Dieter Lelgemann und Andreas Fuls: "Zur hellenistischen Methode der
Bestimmung des Erdumfangs und zur Asienkarte des Klaudios
Ptolemaios.", published in zfv (Zeitschrift für Geodäsie,
Geoinformation und Landmanagment) 128. Jahrgang, Heft 3/2003, S.
211217.
 Reference draws of the Nippur
Cubit at Florencetime.net.
 Proposal to Add Ancient Roman
Weights and Monetary Signs to UCS (Universal Character
Set)
See also