Roman Numeral Converter
Type a number or a Roman numeral below — the tool automatically detects which one you entered and converts it to the other, instantly.
Enter a number or a Roman numeral
How to convert Roman numerals
- Type either a whole number (1 to 3,999) or a Roman numeral into the box above.
- The tool automatically detects which one you entered.
- The converted result appears instantly below, in the other format.
Roman numeral symbol values
| Symbol | Value | Symbol | Value |
|---|---|---|---|
| I | 1 | C | 100 |
| V | 5 | D | 500 |
| X | 10 | M | 1,000 |
| L | 50 |
Symbols are normally written largest to smallest, left to right, and their values add together (VI = 6). When a smaller symbol appears before a larger one, it's subtracted instead (IV = 4, IX = 9) — this subtractive notation avoids repeating any symbol more than three times in a row.
FAQ
Is this Roman numeral converter really free, with no sign-up?+
Yes. The tool runs entirely with JavaScript in your browser — there's no account, no API key, and no limit on how often you can use it.
What range of numbers can be converted?+
Standard Roman numerals represent whole numbers from 1 to 3,999. There is no standard way to write 0 or negative numbers, and numbers above 3,999 traditionally require special notation not handled here.
How does the tool know if I typed a number or a Roman numeral?+
It checks whether your input is made up only of digits (a number) or only of the letters I, V, X, L, C, D and M (a Roman numeral), and converts in the matching direction automatically.
What happens if I type an invalid Roman numeral?+
The tool validates the structure of the Roman numeral against the standard rules and shows a message if it isn't a valid, properly formed numeral.
Why do some numbers use subtractive notation, like IV for 4?+
Subtractive notation avoids repeating a symbol four times in a row. Instead of IIII for 4, a smaller-value symbol placed before a larger one (I before V) means "subtract," giving IV.
Tools for Number Conversion
How This Converter Works
Your value is converted live between numbers and Roman numerals with JavaScript using the standard conversion rules — nothing you enter is uploaded to a server or stored anywhere.
Last updated: August 28, 2026.
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