🏛️ Roman Numeral Converter
2026 = MMXXVI. Type in either box and the other updates, with proper validation, so "IIII" and "IC" are flagged with their canonical spellings instead of silently accepted.
2026 = MMXXVI
Standard (subtractive) notation: I=1, V=5, X=10, L=50, C=100, D=500, M=1000; IV=4, IX=9, XL=40, XC=90, CD=400, CM=900. Malformed numerals like "IIII" or "IC" are rejected with the canonical spelling suggested. Converts locally.
How the roman numeral converter works
Number to numeral uses the standard subtractive notation: work down through M (1000), CM (900), D (500), CD (400), C, XC, L, XL, X, IX, V, IV, I, appending symbols greedily, 2026 becomes MM + XX + VI. Numeral to number reads left to right, subtracting a symbol when a larger one follows it (IX = 9) and adding otherwise, then the tool re-encodes the result and compares: if your input wasn't the canonical spelling ("IIII", "VX", "IC"), it's rejected with the correct form suggested, rather than silently interpreted. Standard notation covers 1-3999.
The validation is the differentiator: most converters happily accept "IIII" or even nonsense like "IC" (99 is XCIX, subtractive pairs only allow I before V/X, X before L/C, C before D/M). Strictness matters when you're checking an inscription, a movie copyright year (MCMXCIX = 1999), or a Super Bowl number. Above 3999 the Romans used an overline (vinculum) multiplying by 1000, outside standard notation, so this tool stops at 3999 and says so.
Frequently asked questions
What are the Roman numeral symbols?
I=1, V=5, X=10, L=50, C=100, D=500, M=1000. A smaller symbol before a larger one subtracts, in six allowed pairs only: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.
Why is 1999 MCMXCIX and not MIM?
Subtractive pairs are restricted: I may precede only V and X, X only L and C, C only D and M. So 1999 = M + CM + XC + IX. "MIM" breaks the rule, and this converter will tell you so.
What's the largest standard Roman numeral?
MMMCMXCIX = 3999. Larger numbers historically used a vinculum (overline meaning ×1000), a different notation beyond the standard system this tool implements.
Why does it reject numerals other converters accept?
It re-encodes your input's value and requires the spellings to match, the definition of well-formed. Loose inputs like IIII (clock faces aside) get the canonical form suggested rather than a silent guess.
Does it work offline?
Yes, conversion is pure local logic.