Roman Numeral Converter
Convert between Arabic numbers (1–3999) and Roman numerals in both directions, live as you type. Invalid numerals — bad letters, too many repeats or illegal subtractive pairs — are rejected with a clear message.
The seven letters
| Letter | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
Worked examples
| Number | Roman |
|---|---|
| 1994 | MCMXCIV |
| 58 | LVIII |
| 2026 | MMXXVI |
How to use
- Type a number between 1 and 3999 to see its Roman numeral instantly.
- Or type a Roman numeral — letters I, V, X, L, C, D, M — to convert it back to a number.
- Check the reference tables below for the value of each letter and worked examples.
Frequently asked questions
What is the largest number Roman numerals can express?
With the standard seven letters and subtractive notation, the largest value is 3,999, written MMMCMXCIX. Ancient Romans sometimes drew a bar over a numeral to multiply it by 1,000, but that convention is not part of the modern standard, so converters — including this one — stop at 3,999.
What makes a Roman numeral invalid?
Three common mistakes: repeating V, L or D (these are never repeated); repeating any letter more than three times in a row; and using subtractive pairs that do not exist. Only IV, IX, XL, XC, CD and CM are legal subtractions — combinations like IC, IL, XM or VX are rejected by this tool with an explanatory error.
Why is there no zero or negative number?
Roman numerals grew out of tallying and additive counting, so the system simply has no symbol for zero and no way to mark a negative. Zero arrived in Europe through the Hindu-Arabic decimal system. If you enter 0 or a number outside 1–3999, this tool explains the valid range instead of guessing.
Are lowercase roman numerals accepted?
Yes — input is normalized to uppercase before validation, so xiv, XIV and XiV all convert to 14. The output is always produced in uppercase, which is the standard written form. Watch out for copy-pasted text that looks like letters but contains lookalike characters; those will be reported as invalid.
Where are Roman numerals still used today?
You will meet them on clock faces, in book chapters and film sequels, on building cornerstones, in the names of monarchs and popes, and in the yearly Super Bowl numbering. They survive as a compact, decorative notation — and as a reminder that a numeral system does not need a place-value zero to last two thousand years.