Type a number or a Roman numeral into either field and the other updates. Roman numerals are validated strictly — non-standard forms like "IIII" for 4 are rejected in favor of the standard "IV".
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Roman Numeral Converter
Convert between numbers (1–3999) and Roman numerals.
How this works & FAQ
How do I convert a number to Roman numerals?
Type the number into the Number field above and the Roman numeral appears instantly in the field below — no button click needed.
What is the largest number I can convert to Roman numerals?
Standard Roman numerals go up to 3999 (MMMCMXCIX). There's no standard single-letter symbol for 4000 and above without special notation, so this converter accepts 1-3999.
Why is "IIII" not accepted for the number 4?
This converter enforces standard subtractive notation, where 4 is written "IV" and 9 is written "IX". Repeating a numeral four times in a row (like "IIII") is non-standard and gets rejected.