Roman numerals

Roman numerals are used to paginate (place page numbers) in forewords and other preliminaries as well as for appendices. Mostly lower case characters are used for this purpose.

Dates of issue are also presented in roman numerals (upper case characters). This is common in older (before 1900) printed books, but you may find this also in modern books.

Characters used for roman numerals

Roman inscriptions are mostly on stone and the script used uppercase only (Capitalis Romana). Lower case characters are medieval 'inventions'.

Value	Character	Value	Character
1	i or I	5	v or V
10	x or X	50	l or L
100	c or C	500	d or D
1000	m or M

Arrangement of characters

Although the historical practice has varied, the modern convention arranges the letters from left to right in order of decreasing value; the total is then calculated by adding the numerical values of all the letters in the sequence. This can be summarised with the following rules:

1. Unit values (I, X, C or M) may be repeated up to three times
2. Intermediate values (V, L, D) may not be repeated
3. To represent values 4 and 9, the lower unit is placed left to the higher unit denoting a subtraction. This is to generate shorter numeral sequences.

The subtraction principle (3) is quite restrictive:
The smaller number must be a power of ten (I, X or C) and precede a number no larger than 10 times its own value. The smaller number itself can be preceded only by a number at least 10 times greater (e.g. LXC is invalid) and it must also be larger than any numeral that follows the one from which it is being subtracted (e.g. CMD is invalid).

value	character	arrangement
1 … 3	repeated characters	I, II, III; XI, XIII; MCCC
4	lower value before intermediate value	IV, XL, XC…
5	intermediate value	V, L, D
6 … 8	lower value after intermediate value	VI, VII, VIII, LX, LXX, LXX
9	lower value before higher value	IX,XC, CM

Examples

value	correct arrangement	incorrect arrangement
15	XV	XIIIII
28	XXVIII	XXIIX
49	XLIX	ILX
99	XCIX	IC
1401	MCDI	MCCCCI
1599	MDXCIX	IMD, MDIC
1999	MCMXCIX	IMM
3999	MMMCMXCIX	largest possible roman numeral with the rules noted above.

Some scholars claim that it is allowed to place 4 M's providing the greatest possible numeral to be 4999 (MMMMCMXCIX).

Further links

• Of course: Wikipedia
• Visual Roman Numeral Converter
• Roman Numeral Charts
• Purplemath
• LiveScience
• Know The Romans
• On Roman Numerals contains a nice conversion calculator (JavaScript)
• Roman Numerals, History and Use