About Roman numerals

Roman numerals represent integers by combining the symbols I, V, X, L, C, D, and M.

Standard Roman numerals can represent integers from 1 to 3999. There is no symbol for 0.

1234 = MCCXXXIV
3999 = MMMCMXCIX

Basic symbols

Roman numerals use the following seven symbols.

Additive notation

When symbols are written from larger values to smaller values, their values are added.

VIII = 5 + 1 + 1 + 1 = 8
LX = 50 + 10 = 60
MDC = 1000 + 500 + 100 = 1600

I, X, C, and M may be repeated up to three times in a row. V, L, and D are used only once in the same digit position.

Subtractive notation

When a smaller symbol is placed immediately before a larger symbol, the smaller value is subtracted. Standard Roman numerals use the following six subtractive forms.

44 = XLIV
999 = CMXCIX
1999 = MCMXCIX

Forms such as IC for 99, IL for 49, or VX for 5 are not standard, so they are not supported.

History of Roman numerals

Roman numerals are thought to have developed in ancient Rome from simple marks and tally-like notches used for counting. A vertical stroke such as I came to represent 1, separate symbols came to represent groups of 5 and 10, and the system was eventually organized around combinations of V, X, L, C, D, and M.

Early Roman numerals were not as strictly standardized as they are today. For example, 4 was sometimes written as IIII as well as IV, and 9 was sometimes written as VIIII instead of IX. The subtractive forms commonly used today, such as IV, IX, XL, XC, CD, and CM, were standardized later.

Roman numerals were used for a long time in commerce, inscriptions, calendars, clocks, and chapter numbers. They remain in use today as decorative and conventional notation for years and numbering.