How to Do a Roman Numeral on the Computer

By Jess Kroll

Roman numerals were long used as the standard system of numeration throughout much of the world. The system's usage even persists today in limited applications, such as years of copyright for published works, and in some movie and ship names. While current number systems are based on Arabic numerals, which unlike the Roman system uses a base of ten and has a number for nothing (0), Roman numerals are used as standard alphabetic characters. This usage makes them easy to write on a computer.

Step 1

Learn the Roman system of numeration. The Roman number system begins with a capital "i" ("I") as 1; "II" as 2; and "III" as 3, before shifting to "IV" as 4; "V" as 5; and "VI" as six. Other numbers include L for 50; C for 100; D for 500; and M for 1,000. The pattern of subtracting the smaller number from the larger continues whenever one character increases to another. For example: 9 is written as "IX" (10 - 1); 40 is "XL" (50 - 10); and 900 is CM (1000 - 100). However, 999 is "CMXCIX" (1000 - 100 + 100 - 10 + 10 - 1), and not "IM."

Step 2

Set the "Caps Lock" or use the "Shift" key when writing the letter of the Roman numeral. Lower case Roman numerals are typically used only for literary purposes, as in denoting subsections, outlining the "Forward" or "Preface" sections of a book, or to numerate multiple appendices.

Step 3

Translate the number into Roman characters. For example, when writing 469 remember that 400 is written as CD (500 - 100); 60 as LX (50 + 10); and 9 as IX (10 -1). Remember that single numbers are always the same, thus 469 can't ever be written as CDILXX (literally 500 - 100 - 1 + 50 + 10 +10) or XXXID (500 - 10 - 10 - 10 - 1).

Step 4

Type out the letters as they appear in the number in capitals -- 469 is written as CDLXIX. As further example, 42 is XLII, 248 is CCXLVIII and 1979 is written as MCMLXXIX.

Tips & Warnings

  • Any number lower than "M" repeats no more than three times. With the fourth occurrence, it is written as subtraction from a higher numeral.