Roman Numeral Converter - Arabic ↔ Roman Numerals

How Roman numerals work

Roman numerals use seven letters: I (1), V (5), X (10), L (50), C (100), D (500), and M (1,000). Numerals are generally written from largest to smallest, left to right, and values are added together. The special cases are the six subtractive pairs:

• IV = 4 (5 − 1)
• IX = 9 (10 − 1)
• XL = 40 (50 − 10)
• XC = 90 (100 − 10)
• CD = 400 (500 − 100)
• CM = 900 (1,000 − 100)

Roman numerals reference table 1–20

Roman numerals reference table for hundreds and thousands

Common uses of Roman numerals today

Roman numerals are still widely used for: clock faces (I–XII), chapter and book numbering, movie sequel numbering (e.g., Rocky IV), Super Bowl numbering, Olympic Games years, copyright years on film and TV credits, and formal outlines.

Why do clock faces show IIII instead of IV?

Many clock faces use IIII instead of IV. Theories include: aesthetic balance (four I's mirror the VIII on the opposite side), avoiding confusion with the Roman numeral for "Jupiter" (IV was an abbreviation), and a historical preference by clockmakers. This converter uses standard academic notation (IV for 4).

Medieval and modern extensions

Standard Roman numerals max out at 3,999 (MMMCMXCIX). To represent larger numbers, medieval scribes used a vinculum (overbar) to multiply a numeral by 1,000:

• V̄ = 5,000
• X̄ = 10,000
• L̄ = 50,000
• C̄ = 100,000
• D̄ = 500,000
• M̄ = 1,000,000

This tool follows the modern convention (maximum 3,999).

Year conversion reference