Roman Numeral Converter
Convert numbers to roman numerals and roman numerals back to numbers.
All calculations happen locally in your browser — nothing is uploaded, stored or tracked.
Pick a direction
Number to roman, or roman to number.
Enter the value
1–3,999 for numbers; valid letters for roman.
Read the result
The conversion appears instantly.
What Is a Roman Numeral Converter?
Roman numerals use seven letters — I, V, X, L, C, D and M — to represent 1, 5, 10, 50, 100, 500 and 1,000. Numbers are built by combining letters, with a subtractive rule: a smaller letter before a larger one is subtracted (IV is 4, IX is 9).
The converter handles numbers from 1 to 3,999 (the largest number expressible with standard roman numerals) in both directions. The roman-to-number mode validates the input and rejects malformed numerals.
The Conversion Rules
Conversion works from the largest value down: 1,989 becomes M (1000), CM (900), LXXX (80), IX (9) → MCMLXXXIX.
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Every calculation on this site runs in your browser using vanilla JavaScript. Nothing is uploaded, stored or tracked.
- 100% local, client-side calculations
- No data stored on any server
- No tracking, no analytics, no ads scripts
- Works offline once loaded
Frequently Asked Questions
How do I write 1999 in roman numerals?
MCMXCIX: M (1000) + CM (900) + XC (90) + IX (9).
Why is 4 written IV and not IIII?
The subtractive rule: a smaller numeral before a larger one is subtracted. IV means 5 − 1.
What is the largest roman numeral?
With standard notation, 3,999 (MMMCMXCIX). Numbers beyond that require overline notation, which is not supported here.
Can I convert lowercase roman numerals?
Yes — the converter accepts both cases, e.g. "xiv" equals 14.
How do I convert years like MMXXIV?
Enter the roman numerals in the roman-to-number mode: MMXXIV = 2024.