Roman numerals are a numeral system of ancient Rome based on letters of the alphabet, which are combined to signify the sum (or in some cases, the difference) of their values. The first ten Roman numerals are
The Roman numeral system is decimal^{[1]} but not directly positional and does not include a zero. It is a cousin of the Etruscan numerals, and the letters derive from earlier nonalphabetical symbols; over time the Romans came to identify the symbols with letters of the Latin alphabet. The system was modified slightly during the Middle Ages to produce the system used today.
Roman numerals are commonly used in numbered lists (such as the outline format of an article), clock faces, pages preceding the main body of a book, chord triads in music analysis, dated notices of copyright, months of the year, successive political leaders or children with identical names, and the numbering of annual events. See modern usage below.
For arithmetic involving Roman numerals, see Roman arithmetic and Roman abacus.
Numeral systems by culture  

HinduArabic numerals  
Eastern Arabic Indian family Khmer 
Mongolian Thai Western Arabic 
East Asian numerals  
Chinese Counting rods Japanese 
Korean Suzhou Vietnamese 
Alphabetic numerals  
Abjad Armenian Āryabhaṭa Cyrillic 
Ge'ez Greek (Ionian) Hebrew 
Other systems  
Attic Babylonian Brahmi Egyptian Etruscan Inuit 
Mayan Quipu Roman Urnfield 
List of numeral system topics  
Positional systems by base  
Decimal (10)  
1, 2, 3, 4, 5, 8, 12, 16, 20, 60 more…  
Contents 
Roman numerals are based on seven symbols: a stroke (identified with the letter I) for a unit, a chevron (identified with the letter V) for a five, a crossstroke (identified with the letter X) for a ten, a C (identified as an abbreviation of Centum) for a hundred, etc.:
Symbol  Value 

I  1 (one) (unus) 
V  5 (five) (quinque) 
X  10 (ten) (decem) 
L  50 (fifty) (quinquaginta) 
C  100 (one hundred) (centum) 
D  500 (five hundred) (quingenti) 
M  1000 (one thousand) (mille) 
Symbols are iterated to produce multiples of the decimal (1, 10, 100, 1000) values, with V, L, D substituted for a multiple of five, and the iteration continuing: I "1", II "2", III "3", V "5", VI "6", VII "7", etc., and the same for other bases: X "10", XX "20", XXX "30", L "50", LXXX "80"; CC "200", DCC "700", etc. At the fourth iteration, a subtractive principle may be employed, with the base placed before the higher base: IIII or IV "4", VIIII or IX "9", XXXX or XL "40", LXXXX or XC "90", CCCC or CD "400", DCCCC or CM "900".
The Romans only used what is called capital (upper case) letters in modern usage. In the Middle Ages, minuscule (lower case) letters were developed, and these are commonly used for Roman numerals: i, ii, iii, iv, etc. Also in medieval use was the substitution of j for a final i to end numbers, such as iij for 3 or vij for 7. This was not a separate letter, but merely a swash variant of i. It is used today, especially in medical prescriptions, to prevent tampering with or misinterpretation of the numbers after they are written.^{[2]} ^{[3]}
For large numbers (4000 and above), a bar can be placed above a base numeral, or parentheses placed around it, to indicate multiplication by 1000, although the Romans themselves often just wrote out the "M"s:^{[4]}
Symbol  Value 

V or (V)  five thousand 
X or (X)  ten thousand 
L or (L)  fifty thousand 
C or (C)  one hundred thousand 
D or (D)  five hundred thousand 
M or (M)  one million 
The parentheses are more versatile; (II) is synonymous with MM, but II is not found.
The basic multiples of Roman numerals thus follow a pattern:
×1  ×2  ×3  ×4  ×5  ×6  ×7  ×8  ×9  

Ones  I  II  III  IV  V  VI  VII  VIII  IX 
Tens  X  XX  XXX  XL  L  LX  LXX  LXXX  XC 
Hundreds  C  CC  CCC  CD  D  DC  DCC  DCCC  CM 
Thousands  M  MM  MMM  IV  V  VI  VII  VIII  IX 
Ten thousands  X  XX  XXX  XL  L  LX  LXX  LXXX  XC 
Hundred thousands  C  CC  CCC  CD  D  DC  DCC  DCCC  CM 
A practical way to write a Roman number is to consider the modern Arabic numeral system, and separately convert the thousands, hundreds, tens, and ones as given in the chart above. So, for instance, 1234 may be thought of as "one thousand and two hundreds and three tens and four", obtaining M (one thousand) + CC (two hundreds) + XXX (thirty) + IV (four), for MCCXXXIV. Thus eleven is XI (ten and one), 32 is XXXII (thirty and two) and 2009 is MMIX (two thousand and nine). Note that the subtractive principle is not extended beyond the chart: for example, IL is not used for 49, rather this should be written as forty (XL) and nine (IX), or XLIX.
Although the Roman numerals are now written with letters of the Roman alphabet, they were originally independent symbols. The Etruscans, for example, used I Λ X ⋔ 8 ⊕ for I V X L C M, of which only I and X happened to be letters in their alphabet. One folk etymology has it that the V represented a hand, and that the X was made by placing two Vs on top of each other, one inverted. However, the EtruscoRoman numerals actually appear to derive from notches on tally sticks, which continued to be used by Italian and Dalmatian shepherds into the 19th century.^{[5]}
Thus, 'I' descends not from the letter 'I' but from a notch scored across the stick. Every fifth notch was double cut (i.e. ⋀, ⋁, ⋋, ⋌, etc.), and every tenth was cross cut (X), IIIIΛIIIIXIIIIΛIIIIXII..., much like European tally marks today. This produced a positional system: Eight on a counting stick was eight tallies, IIIIΛIII, or the eighth of a longer series of tallies; either way, it could be abbreviated ΛIII (or VIII), as the existence of a Λ implies four prior notches. By extension, eighteen was the eighth tally after the first ten, which could be abbreviated X, and so was XΛIII. Likewise, number four on the stick was the Inotch that could be felt just before the cut of the Λ (V), so it could be written as either IIII or IΛ (IV). Thus the system was neither additive nor subtractive in its conception, but ordinal. When the tallies were transferred to writing, the marks were easily identified with the existing Roman letters I, V, X
The tenth V or X along the stick received an extra stroke. Thus 50 was written variously as N, И, K, Ψ, ⋔, etc., but perhaps most often as a chickentrack shape like a superimposed V and I  ᗐ. This had flattened to ⊥ (an inverted T) by the time of Augustus, and soon thereafter became identified with the graphically similar letter L. Likewise, 100 was variously Ж, ⋉, ⋈, H, or as any of the symbols for 50 above plus an extra stroke. The form Ж (that is, a superimposed X and I) came to predominate. It was written variously as >I< or ƆIC, was then abbreviated to Ɔ or C, with C variant finally winning out because, as a letter, it stood for centum, Latin for "hundred".
The hundredth V or X was marked with a box or circle. Thus 500 was like a Ɔ superimposed on a ⋌ or ⊢ — that is, like a Þ with a cross bar,— becoming D or Ð by the time of Augustus, under the graphic influence of the letter D. It was later identified as the letter D, perhaps as an abbreviation of demimille "halfthousand"; this at least was the folk etymology given to it later on.
Meanwhile, 1000 was a circled or boxed X: Ⓧ, ⊗, ⊕, and by Augustinian times was partially identified with the Greek letter Φ phi. In different traditions it then evolved along several different routes. Some variants, such as Ψ and ↀ, were historical dead ends, although folk etymology later identified D for 500 as graphically half of Φ for 1000 because of the CD variant. A third line, ↀ, survives to this day in two variants:
In general, the number zero did not have its own Roman numeral, but a primitive form (nulla) was known by medieval computists (responsible for calculating the date of Easter). They included zero (via the Latin word nulla meaning "none") as one of nineteen epacts, or the age of the moon on March 22. The first three epacts were nulla, xi, and xxii (written in minuscule or lower case). The first known computist to use zero was Dionysius Exiguus in 525. Only one instance of a Roman numeral for zero is known. About 725, Bede or one of his colleagues used the letter N, the initial of nulla, in a table of epacts, all written in Roman numerals.
Though the Romans used a decimal system for whole numbers, reflecting how they counted in Latin, they used a duodecimal system for fractions, because the divisibility of twelve (12 = 3 × 2 × 2) makes it easier to handle the common fractions of 1/3 and 1/4 than does a system based on ten (10 = 2 × 5). On coins, many of which had values that were duodecimal fractions of the unit as, they used a tallylike notational system based on twelfths and halves. A dot • indicated an uncia "twelfth", the source of the English words inch and ounce; dots were repeated for fractions up to five twelfths. Six twelfths (one half) was abbreviated as the letter S for semis "half". Uncia dots were added to S for fractions from seven to eleven twelfths, just as tallies were added to V for whole numbers from six to nine.
Each of these fractions had a name, which was also the name of the corresponding coin:
Fraction  Roman Numeral  Name (nominative and genitive)  Meaning 

1/12  •  uncia, unciae  "ounce" 
2/12 = 1/6  •• or :  sextans, sextantis  "sixth" 
3/12 = 1/4  ••• or ∴  quadrans, quadrantis  "quarter" 
4/12 = 1/3  •••• or ::  triens, trientis  "third" 
5/12  ••••• or :•:  quincunx, quincuncis  "fiveounce" (quinque unciae → quincunx) 
6/12 = 1/2  S  semis, semissis  "half" 
7/12  S•  septunx, septuncis  "sevenounce" (septem unciae → septunx) 
8/12 = 2/3  S•• or S:  bes, bessis  "twice" (as in "twice a third") 
9/12 = 3/4  S••• or S:•  dodrans, dodrantis or nonuncium, nonuncii 
"less a quarter" (dequadrans → dodrans) or "ninth ounce" (nona uncia → nonuncium) 
10/12 = 5/6  S•••• or S::  dextans, dextantis or decunx, decuncis 
"less a sixth" (desextans → dextans) or "ten ounces" (decem unciae → decunx) 
11/12  S••••• or S:•:  deunx, deuncis  "less an ounce" (deuncia → deunx) 
12/12 = 1  I  as, assis  "unit" 
The arrangement of the dots was variable and not necessarily linear. Five dots arranged like :·: (as on the face of a die) are known as a quincunx from the name of the Roman fraction/coin. The Latin words sextans and quadrans are the source of the English words sextant and quadrant.
Other Roman fractions include:
The notation of Roman numerals has varied through the centuries. Originally, it was common to use IIII to represent four, because IV represented the Roman god Jupiter, whose Latin name, IVPPITER, begins with IV. The subtractive notation (which uses IV instead of IIII) has become the standard notation only in modern times. For example, Forme of Cury, a manuscript from 1390, uses IX for nine, but IIII for four. Another document in the same manuscript, from 1381, uses IV and IX. A third document in the same manuscript uses IIII, IV, and IX. Constructions such as IIIII for five, IIX for eight or VV for 10 have also been discovered. Subtractive notation arose from regular Latin usage: the number 18 was duodeviginti or “two from twenty”; the number 19 was undeviginti or "one from twenty". The use of subtractive notation increased the complexity of performing Roman arithmetic, without conveying the benefits of a full positional notation system.
Likewise, on some buildings it is possible to see MDCCCCX, for example, representing 1910 instead of MCMX – notably Admiralty Arch in London. The Leader Building in Cleveland, Ohio, at the corner of Superior Avenue and E.6th Street, is marked MDCCCCXII, representing 1912 instead of MCMXII. Another notable example is on Harvard Medical School's Gordon Hall, which reads MDCCCCIIII for 1904 instead of MCMIV. In Dubrovnik, Croatia, a commemorative inscription marking the 1000th anniversary of King Tomislav’s coronation (Croatia’s first King), appears as DCCCCXXV  MDCCCCXXV instead of CMXXV  MCMXXV (925 1925).
Clock faces that are labeled using Roman numerals conventionally show IIII for four o'clock and IX for nine o'clock, using the subtractive principle in one case and not the other. There are many suggested explanations for this, several of which may be true:
Generally, Roman numerals are written in descending order from left to right, and are added sequentially, for example MMVI (2006) is interpreted as 1000 + 1000 + 5 + 1.
Certain combinations employ a subtractive principle, which specifies that where a symbol of smaller value precedes a symbol of larger value, the smaller value is subtracted from the larger value, and the result is added to the total. For example, in MCMXLIV (1944), the symbols C, X and I each precede a symbol of higher value, and the result is interpreted as 1000 plus (1000 minus 100) plus (50 minus 10) plus (5 minus 1).
A numeral for 10^{n} (I, X, or C) may not precede a numeral larger than 10^{n+1}, where n is an integer.^{[citation needed]} That is, I may precede V and X, but not L or C; X may precede L or C, but not D or M. The numerals 5×10^{n} (V, L, or D) may not be followed by a numeral of greater or equal value.^{[citation needed]} Any symbol that appears more than once consecutively may not be followed by a symbol of larger value.
Roman numerals remained in common use until about the 14th century, when they were replaced by HinduArabic numerals (thought to have been introduced to Europe from alAndalus, by way of Arab traders and arithmetic treatises, around the 11th century). The Roman number system is generally regarded as obsolete in modern usage, but is still seen occasionally. Classical numbering is often used to suggest importance or timelessness, or in other cases where an alternate numbering system is useful for clarity. Examples of their current use include:
Sometimes the numerals are written using lowercase letters (thus: i, ii, iii, iv, etc.), particularly if numbering paragraphs or sections within chapters, or for the pagination of the front matter of a book.
Undergraduate degrees at British universities are generally graded using I, IIi, IIii, III for first, upper second (often pronounced "two one"), lower second (often pronounced "two two") and third class respectively.
In chemistry, Roman numerals were formerly used to denote the group in the periodic table of the elements. But there was not international agreement as to whether the group of metals which dissolve in water should be called Group IA or IB, for example, so although references may use them, the international norm has recently switched to Arabic numerals. However, Roman numerals are still used in the IUPAC nomenclature of inorganic chemistry, for the oxidation number of cations which can take on several different positive charges. For example, FeO is iron(II) oxide and Fe_{2}O_{3} is iron(III) oxide. In contrast, Arabic numerals are used to denote the formal oxidation state (which is not always the same as the oxidation number) of positively or negatively charged atoms. They are also used for naming phases of polymorphic crystals, such as ice.
In astronomy, the natural satellites or "moons" of the planets are traditionally designated by capital Roman numerals, at first by order from the center of the planet, as the four Galilean satellites of Jupiter are numbered, and later by order of discovery; e.g., Callisto was "Jupiter IV" or "J IV". Notably, the notation IV was mostly disused by the Romans for its similarity to the first two letters of Jupiter. With recent discoveries—Jupiter currently has 63 known satellites—as well as computerization, this is somewhat disparaged for the minor worlds, at least in computerized listings.
Science fiction, and not astronomy per se, has adopted the use for numbering the planets around a star; e.g., Planet Earth is called "Sol III".
In photography, Roman numerals (with zero) are used to denote varying levels of brightness when using the Zone system.
In earthquake seismology, Roman numerals are used to designate degrees of the Mercalli intensity scale.
In music theory, while scale degrees are typically represented with Arabic numerals, often modified with a caret or circumflex, the triads that have these degrees as their roots are often identified by Roman numerals (as in chord symbols). See also diatonic functions. Uppercase Roman numerals indicate major triads while lowercase Roman numerals indicate minor triads, as the following chart illustrates. Some writers, however, use upper case Roman numerals for both major and minor triads. Lowercase Roman numerals with a degree symbol indicate diminished triads. For example, in the major mode the triad on the seventh scale degree, the leading tone triad is diminished.
Also in music theory, individual strings of stringed instruments, such as the violin, are often denoted by Roman numerals, with higher numbers denoting lower strings. For example I signifies the E string on the violin and the A string on the viola and cello, these being the highest strings, respectively, on each instrument. They are also sometimes used to signify position. In this case, the number in Roman numerals corresponds with the position number. For example, III means third position and V means fifth.
Roman numeral  I  ii  iii  IV  V  vi  vii^{°} 
Scale degree (major mode) 
tonic  supertonic  mediant  subdominant  dominant  submediant  leading tone 
Roman numeral  i  ii^{°}  (♭)III  iv  v  (♭)VI  (♭)VII  vii^{°} 
Scale degree (minor mode) 
tonic  supertonic  mediant  subdominant  dominant  submediant  subtonic  leading tone 
The above uses are customary for Englishspeaking countries. Although many of them are also maintained in other countries, those countries have additional uses for Roman numerals that are not normally employed in Englishspeaking regions.
The French, Hungarian, Italian, Portuguese, Polish, Romanian, Russian, Spanish, Croatian and Catalan languages use capital Roman numerals to denote centuries. For example, XVIII refers to the eighteenth century, so as to avoid confusion between the 18th century and the 1800s. (The Italians also take the opposite approach, basing names of centuries on the digits of the years; quattrocento for example is a common Italian name for secolo XV, the fifteenth century.) Some scholars in Englishspeaking countries have adopted the former method.
In Italy, Poland, Russia, Central Europe, and in Portuguese, Romanian, Croatian and Serbian languages, mixed Roman and Arabic numerals are used to record dates (usually on tombstones, but also elsewhere, such as in formal letters and official documents). Just as an old clock recorded the hour by Roman numerals while the minutes were measured in Arabic numerals, the month is written in Roman numerals while the day is in Arabic numerals: 14.VI 1789 is 14 June 1789. This is how dates are inscribed on the walls of the Kremlin, for example. This method has the advantage that days and months are not confused in rapid notetaking, and that any range of days or months can be expressed without confusion. For instance, VVIII is May to August, while 1.V  31.VIII is 1 May to 31 August.
In Hungary the Roman numbers are used to record the number of the adoped Acts, for example: the XX. Act of 1949 on the Constitution of the Hungarian Republic.
In Eastern Europe, especially the Baltic nations, Roman numerals are used to represent the days of the week in hoursofoperation signs displayed in windows or on doors of businesses. Monday is represented by I, which is the initial day of the week. Sunday is represented by VII, which is the final day of the week. The hours of operation signs are tables composed of two columns where the left column is the day of the week in Roman numerals and the right column is a range of hours of operation from starting time to closing time. The following example hoursofoperation table would be for a business whose hours of operation are 9:30 AM to 5:30 PM on Mondays, Wednesdays, and Thursdays; 9:30 AM to 7:00 PM on Tuesdays and Fridays; and 9:30 AM to 1:00 PM on Saturdays; and which is closed on Sundays.
I  9:30–17:30 
II  9:30–19:00 
III  9:30–17:30 
IV  9:30–17:30 
V  9:30–19:00 
VI  9:30–13:00 
VII  — 
In CIS countries, capital Roman numerals I, II and V still are sometimes used according to the regional standard GOST 2.728–74 (2002), to specify rated resistor power (in watts) in schematic symbols by inscribing the numeral along inside the symbol rectangle.
Since the French use capital Roman numerals to refer to the quarters of the year (III is the third quarter), and this has become the norm in some European standards organisation, the mixed Roman–Arabic method of recording the date has switched to lowercase Roman numerals in many circles, as 4viii1961. (ISO has since specified that dates should be given in all Arabic numerals, in ISO 8601 formats.)
In geometry, Roman numerals are often used to show lines of equal length.
In Hungary, Poland, Romania, Serbia and other European countries to lesser extent, Roman numerals are used for floor numbering. Likewise apartments in central Amsterdam are indicated as 138III, with both an Arabic numeral (number of the block or house) and a Roman numeral (floor number). The apartment on the ground floor is indicated as '138huis'.
In Poland, Roman numerals are used for ordinals in names of some institutions. In particular high schools ("V Liceum Ogólnokształcące w Krakowie"  5th High School in Kraków), tax offices ("II Urząd Skarbowy w Gdańsku"  2nd Office of Treasury in Gdańsk) and courts ("I Wydział Cywilny Sądu Okręgowego"  District Court, 1st Civil Division)  use Roman numerals. Institutions that use "Institution nr N" notation always use Arabic numerals. These include elementary ("Szkoła Podstawowa nr 5") and middle schools ("Gimnazjum nr 5").
Roman numerals are rarely used in Asia. The motion picture rating system in Hong Kong uses categories I, IIA, IIB, and III based on Roman numerals.
In the Middle Ages, Latin writers used a horizontal line above a particular numeral to represent one thousand times that numeral, and additional vertical lines on both sides of the numeral to denote one hundred times the number, as in these examples:
The same overline was also used with a different meaning, to clarify that the characters were numerals. Sometimes both underline and overline were used, e. g. MCMLXVII, and in certain (serif) typefaces, particularly Times New Roman, the capital letters when used without spaces simulates the appearance of the under/over bar, e.g. MCMLXVII.
Sometimes 500, usually D, was written as I followed by an apostrophus or apostrophic C (which resembles a backwards C, i.e. Ɔ), while 1,000, usually M, was written as CIƆ. This is believed to be a system of encasing numbers to denote thousands (imagine the Cs as parentheses). This system has its origins from Etruscan numeral usage. The D and M symbols to represent 500 and 1,000 were most likely derived from IƆ and CIƆ, respectively.
An extra Ɔ denoted 500, and multiple extra Ɔs are used to denote 5,000, 50,000, etc. For example:
Base number  CIƆ = 1,000  CCIƆƆ = 10,000  CCCIƆƆƆ = 100,000  

1 extra Ɔ  IƆ = 500  CIƆƆ = 1,500  CCIƆƆƆ = 10,500  CCCIƆƆƆƆ = 100,500 
2 extra Ɔs  IƆƆ = 5,000  CCIƆƆƆƆ = 15,000  CCCIƆƆƆƆƆ = 105,000  
3 extra Ɔs  IƆƆƆ = 50,000  CCCIƆƆƆƆƆƆ = 150,000 
Sometimes CIƆ was reduced to a lemniscate symbol (ↀ) for denoting 1,000. John Wallis is often credited for introducing this symbol to represent infinity (∞), and one conjecture is that he based it on this usage, since 1,000 was hyperbolically used to represent very large numbers. Similarly, 5,000 (IƆƆ) was reduced to ↁ; and 10,000 (CCIƆƆ) was reduced to ↂ.
In medieval times, before the letter j emerged as a distinct letter, a series of letters i in Roman numerals was commonly ended with a flourish; hence they actually looked like ij, iij, iiij, etc. This proved useful in preventing fraud, as it was impossible, for example, to add another i to vij to get viij.
Most uniquely, during the Middle Ages there came about a unique, more comprehensive shorthand for writing Roman numerals, called today the "medieval Roman numerals." This system used almost every other letter of the Roman alphabet to stand as abbreviations for more longhand numbers (usually those that consisted of repetitions of the same symbol). They are still listed today in most dictionaries, although through disfavor are primarily out of use.^{[8]}
Modern number 
Medieval abbreviation 
Notes 

5  A  Resembles an upsidedown V. Also said to equal 500. 
6  ↅ  Either a ligature of VI, or the Greek letter stigma (Ϛ), having the same numerical value.^{[9]} 
7  S, Z  Presumed abbreviation of septem, Latin for 7. 
11  O  Presumed abbreviation of (e.g.) onze, French for 11. 
40  F  Presumed abbreviation of English forty. 
70  S  Also could stand for 7, and has same etymology. 
80  R  
90  N  Presumed abbreviation of nonaginta, Latin for 90. 
150  Y  Possibly derived from the lowercase y's shape. 
151  K  This unusual abbreviation's origin is unknown; it has also been said to stand for 250. 
160  T  Possibly derived from Greek tetra, as 4 x 40 = 160. 
200  H  
250  E  
300  B  
400  P, G  
500  Q  Redundant with D, abbreviation for quingenti, Latin for 500. 
800  W  More properly, the Greek ω, as W was a fairly new creation. Carried over from Gothic. 
900  ĵ, ↑  Resembled a crooked up arrow. Carried over from Gothic. 
2000  Z 
Some "modern" Roman numerals, postVictorian era, are shown below:
Standard  Arabic  Notes  

none  0  N for nulla was used at least once (by Bede about 725).  
I  1  
II  2  
III  3  
IV  4  IIII is still used on clock and Tarot card faces. See Calendars and clocks above.  
V  5  IIIII was used rarely in the Middle Ages.  
VI  6  
VII  7  
VIII  8  IIX was used rarely in the Middle Ages.  
IX  9  
X  10  VV was used rarely in the Middle Ages.  
XI  11  
XII  12  
XIII  13  
XIV  14  
XV  15  
XVI  16  
XVII  17  
XVIII  18  
XIX  19  
XX  20  
XXI  21  
XXV  25  
XXX  30  
XXXV  35  
XL  40  
XLV  45  
XLIX  49  Per rule above, IL would not be generally accepted.  
L  50  
LX  60  
LXIX  69  
LXX  70  The abbreviation for the Septuagint  
LXXVI  76  
LXXX  80  
XC  90  
XCIX  99  As opposed to the "shortcut" way IC seen above.  
C  100  This is the origin of using the slang term "Cbill" or "Cnote" for "$100 bill" although there is some dispute over this because this is possibly in reference to the French word for 100 which is Cent.  
CL  150  
CC  200  
CCC  300  
CD  400  
CDXCIX  499  Per rule above, ID would not be generally accepted.  
D  500  
DC  600  
DCLXVI  666  Using every symbol except M in descending order gives the beast number.  
DCC  700  
DCCC  800  
CM  900  
CMXCIX  999  Per rule above, IM would not be generally accepted.  
M  1,000  
MCDXLIV  1,444  Smallest pandigital number (each symbol is used)  
MDCLXVI  1,666  Largest efficient pandigital number (each symbol occurs exactly once)  
MCMXC  1,990  Shortcuts like XMM and MXM disagree with the rule stated above  
MCMXCVII  1,997  
MCMXCIX  1,999  Shortcuts like IMM and MIM disagree with the rule stated above  
MM  2,000  
MMI  2,001  
MMX  2,010  
MMD  2,500  
MMM  3,000  
MMMDCCCLXXXVIII  3,888  Longest number (most symbols, without overlines or without extra symbols containing overlines).  
MMMCMXCIX  3,999  Largest number without an overline at any symbol.  
IV  4,000  sometimes MMMM^{[citation needed]} or MV  
V  5,000  
VMDCLXVI  6,666  This number uses every symbol up to V once.  
X  10,000  
L  50,000  
C  100,000  
D  500,000  
M  1,000,000  
MCDXLIV  1,444,000  Smallest pandigital number (each symbol is used with one line above every symbol)  
MDCLXVI  1,666,000  Largest efficient pandigital number (each symbol is used with one line above every symbol)  
MM  2,000,000  
MMMDCCCLXXXVIII  3,888,000  Longest number (most symbols, each symbol is used with one line above every symbol) 
An accurate way to write large numbers in Roman numerals is to handle first the thousands, then hundreds, then tens, then units.
Unicode has a number of characters specifically designated as Roman numerals, as part of the Number Forms^{[10]} range from U+2160 to U+2188. This range includes both upper and lowercase numerals, as well as precombined glyphs for numbers up to 12 (Ⅻ or XII), mainly intended for the clock faces for compatibility with large EastAsian character sets such as JIS X 0213 that provide these characters. The precombined glyphs should only be used to represent the individual numbers where the use of individual glyphs is not wanted, and not to replace compounded numbers. Additionally, glyphs exist for archaic^{[10]} forms of 1000, 5000, 10,000, large reversed C (Ɔ), late 6 (ↅ, similar to Greek Stigma: Ϛ), early 50 (ↆ, similar to down arrow ↓⫝⊥^{[9]}), 50,000, and 100,000. Note that the small reversed c, ↄ is not intended to be used in roman numerals, but as lower case Claudian letter Ↄ,
Code  0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F 

Value^{[11]}  1  2  3  4  5  6  7  8  9  10  11  12  50  100  500  1,000 
U+2160  Ⅰ  Ⅱ  Ⅲ  Ⅳ  Ⅴ  Ⅵ  Ⅶ  Ⅷ  Ⅸ  Ⅹ  Ⅺ  Ⅻ  Ⅼ  Ⅽ  Ⅾ  Ⅿ 
U+2170  ⅰ  ⅱ  ⅲ  ⅳ  ⅴ  ⅵ  ⅶ  ⅷ  ⅸ  ⅹ  ⅺ  ⅻ  ⅼ  ⅽ  ⅾ  ⅿ 
Value  1000  5000  10,000  –  –  6  50  50,000  100,000  
U+2180  ↀ  ↁ  ↂ  Ↄ  ↄ  ↅ  ↆ  ↇ  ↈ 
The characters in the range U+2160–217F are present only for compatibility with other character set standards which provide these characters. For ordinary uses, the standard Latin letters are preferred. Displaying these characters requires a program that can handle Unicode and a font that contains appropriate glyphs for them.
After the Renaissance, the Roman system could also be used to write chronograms. It was common to put in the first page of a book some phrase, so that when adding the I, V, X, L, C, D, M present in the phrase, the reader would obtain a number, usually the year of publication. The phrase was often (but not always) in Latin, as chronograms can be rendered in any language that utilises the Roman alphabet.
The basic modern Latin alphabet  

Aa  Bb  Cc  Dd  Ee  Ff  Gg  Hh  Ii  Jj  Kk  Ll  Mm  Nn  Oo  Pp  Rr  Ss  Tt  Uu  Vv  Ww  Xx  Yy  Zz  
history • palaeography • derivations • diacritics • punctuation • numerals • Unicode • list of letters • ISO/IEC 646 
A Roman numeral is the name for a number when it is written in the way the Romans used to write numbers. Roman numerals are not used very often today in the west. They are used to write the names of kings and queens, or popes. For example: Queen Elizabeth II. They may be used to write the year a book or movie was made.
Contents 
I  1
V  5
X  10
L  50
C  100
D  500
M  1000
If a lower value symbol is before a higher value one, it is subtracted. Otherwise it is added.
So 'IV' is '4' and 'VI' is '6'.
For the numbers above X, only the symbol right before it may be subtracted: so 99 is: XCIX (and not IC).
Numbers are written as Roman numerals in this way:
I = 1
II = 2
III = 3
IV = 4
V =5
VI = 6
VII = 7
VIII = 8
IX = 9
X = 10
XI = 11
XV = 15
XVI = 16
XIX = 19
XX = 20
XXX = 30
XL = 40
L = 50
LX = 60
LXI = 61
XC = 90
C = 100
CD = 400
D = 500
CM = 900
CMXC = 990
CMXCIX = 999
M = 1,000
MCMXCIX = 1,999
MM = 2,000
MMVII = 2007
MMVIII = 2008
MMIX = 2009
MMX = 2010
The System that is in use today is: Whenever the same symbol is written four times, it is replaced by subtracting it from the next higher number (5,50,50,500). That way, IV is written instead of IIII (4), XL instead of XXXX (40), etc.
Usually only one number is subtracted, not two. So 8 is always VIII and never IIX
Especially on clocks and watches, IIII can sometimes still be found. This is done partly because the IIII for the 4 o'clock position aesthetically balances the VIII for the 8 o'clock position.
Proper form is to subtract only a value with the next lower power of 10. Thus, 900 is written CM, but 990 would not be XM  properly, it is CM for the 900 portion and XC for the 90 portion, or CMXC. Similarly, 999 would not be IM but rather CMXCIX  CM for the 900 portion, XC for the 90 portion, and IX for the 9 portion. Only values with 1's are ever used to subtract; 45 is properly XLV, not VL.
Notations in Roman numerals for numbers higher than 3,001 are rarely seen. One system utilizes V and X with bars over them to signify 5,000 and 10,000, respectively.
