Roman Numerals Converter
Convert Arabic numbers to Roman numerals and vice versa. Supports values from 1 to 3999. Instant bidirectional conversion.
How do Roman numerals work?
Seven letters hold up the whole system: I (1), V (5), X (10), L (50), C (100), D (500) and M (1000). When a smaller letter sits before a larger one, it subtracts, and that is how we get 4 (IV), 9 (IX), 40 (XL), 90 (XC), 400 (CD) and 900 (CM).
Values run from 1 up to 3999 (MMMCMXCIX). Worth remembering that the classical Roman system had no zero and no negative numbers.
Roman numerals: symbols and rules
Roman numerals use seven symbols: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Values are written from largest to smallest and added together — MCLXVI = 1000+100+50+10+5+1 = 1166. When a smaller symbol appears before a larger one, it is subtracted: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900. Example: MCMXCIX = 1000 + (1000−100) + (100−10) + (10−1) = 1999.
Rules: never repeat the same symbol more than three times in a row (4 is IV, not IIII — although clock faces traditionally use IIII for visual symmetry); only I, X and C can be used subtractively, and only before the next two larger symbols (I before V or X; X before L or C; C before D or M). There is no zero in Roman numerals. The practical limit is 3999 (MMMCMXCIX); larger numbers use a vinculum — a bar above the symbol that multiplies its value by 1000.
Where Roman numerals still appear
Book prefaces and chapter numbering, names of kings and popes (Louis XIV, John Paul II), Super Bowl editions (LVIII = 58), Olympic Games, clock and watch faces, copyright dates in films and TV credits (MCMXCIX = 1999), monuments and cornerstones, outlines and legal documents. They survive because they look formal and visually distinguish enumerated items from cardinal numbers.
FAQ
Is there a Roman numeral for zero? No. The Romans had no symbol for zero. Medieval scholars sometimes wrote nulla or N, but it is not part of the standard system.
Why does IIII appear on clocks instead of IV? Tradition and symmetry. IIII balances visually with VIII on the opposite side of the dial and avoids confusion with VI when read upside down.
How do you write very large numbers? A bar (vinculum) above a numeral multiplies it by 1000 — so V̄ = 5000 and M̄ = 1,000,000.
Can I write 1999 as MIM? No. Only I, X and C can subtract, and only from the next two larger symbols. The correct form is MCMXCIX.
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Convert Roman numerals
Old clocks, book chapters, kings' names, dates carved into monuments. Roman numerals are still around, and reading or writing one correctly takes a bit of effort. Here you can go both ways: Arabic to Roman and Roman back to Arabic.
The conversion covers values from 1 to 3999, the range the classic Roman system can represent, and it follows the subtraction rules (IV is 4, IX is 9). Handy when you want to decode a date in Roman numerals, number chapters, put together a logo or just check that you spelled it right.
Type the number in either format and the equivalent shows up right below. Everything happens in your own browser, with nothing to install.