Roman Numeral Calculator
Convert between Roman numerals and Arabic numbers with detailed symbol breakdown and conversion rules explanation.
How do Roman numerals work?
Roman numerals use seven letters: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Rules: 1) Add when larger/equal comes before smaller (VI=6). 2) Subtract when smaller comes before larger (IV=4). 3) Only subtract powers of 10 (I, X, C). 4) Never subtract more than one numeral or repeat subtraction (99=XCIX not IC). 5) Don't repeat V, L, D. Max repeat of I, X, C, M is 3 (4=IV not IIII, except on clocks).
Why is 4 written as IV and not IIII?
Subtractive notation (IV) became standard in medieval times for efficiency, though IIII appears on some clock faces for symmetry/tradition. Rules: I before V or X (4=IV, 9=IX), X before L or C (40=XL, 90=XC), C before D or M (400=CD, 900=CM). This prevents long repetitions: 49=XLIX (not XXXXVIIII), 444=CDXLIV. Exception: Clock faces often use IIII for visual balance with VIII.
What is the largest number in Roman numerals?
Standard Roman numerals go to 3,999 (MMMCMXCIX). Ancient Romans used vinculum (overline) for *1000: VÌ„=5000, XÌ„=10000. Without vinculum, modern standard limits at 3,999 because you can't repeat M more than 3 times and there's no symbol for 5,000 in basic system. Some systems use double parentheses or other notation for larger numbers, but 1-3,999 is universally accepted range.
Can you write zero in Roman numerals?
No, Roman numerals have no zero. Ancient Romans used word "nulla" (none) instead. Roman system is additive/subtractive, not positional like Arabic numerals where zero is placeholder. They didn't need zero for counting (I, II, III...) or basic arithmetic. This limitation (plus no fractions except 1/12) made complex calculations difficult, contributing to Roman abacus use and eventual adoption of Arabic numerals in medieval Europe.
Where are Roman numerals still used today?
Modern uses: 1) Clock faces (Big Ben, watches). 2) Copyright years (©MMXXIV=2024). 3) Outlines/lists (I, II, III, IV). 4) Movie sequels (Rocky IV). 5) Super Bowl (LIX=59). 6) Royalty/popes (Elizabeth II, Pope Francis). 7) Book chapters/prefaces. 8) Building dates on cornerstones. 9) Formal documents. Benefits: traditional, elegant, hard to alter fraudulently, culture/prestige.