Type a number or a Roman numeral to convert instantly — then try the quiz below.
Converter
Quiz — 10 questions
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How Roman numerals work
Seven letters carry all the values: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Values add from left to right (VIII = 8), but a smaller value before a larger one subtracts (IV = 4, IX = 9, XL = 40, CM = 900) — only I, X and C can be used that way. Numerals still appear on clock faces, book chapters, movie sequels and events like Super Bowl LVIII, so reading them fluently is a small skill that keeps paying off. The quiz mixes both directions and gets you fluent fast.
Standard Roman numerals repeat a letter at most three times, so MMMCMXCIX (3999) is the largest normal form. The Romans wrote bigger numbers with a bar over letters (V̄ = 5000), but that notation isn't standard today.
Why is 4 written IV and not IIII?
Subtractive notation (IV = 5−1) became the standard because it's shorter. Fun exception: many clock faces still use IIII for visual balance with VIII on the opposite side of the dial.
Is there a Roman numeral for zero?
No — the classical system has no symbol for zero, since it counts things rather than positions. Medieval scholars later used the word "nulla" (or the letter N) in tables, but it was never part of standard Roman notation.
Why is 99 written XCIX and not IC?
The subtraction rule only allows six pairs: IV, IX, XL, XC, CD, CM — you can only subtract I, X or C from the next two steps up. So 99 = XC (90) + IX (9), and 1999 is MCMXCIX rather than MIM.
Why do movies, kings and the Super Bowl use Roman numerals?
Tradition and gravitas: monarchs and popes have been numbered that way for centuries (Elizabeth II, Louis XIV), film credits adopted them for copyright years, and the Super Bowl uses them (LVIII = 58) so each edition reads as a grand title rather than a plain number.