MMXXIV
About Roman Numeral Converter — Numbers to Roman & Back
Roman numerals build numbers from seven letters — I, V, X, L, C, D, and M — combined with simple additive and subtractive rules. They still show up on clock faces, in book chapters and outlines, on monuments and movie copyright dates, and after monarchs' and popes' names. Reading or writing them by hand is easy to get wrong, especially around subtractive forms like IV (4) and IX (9).
This free Roman numeral converter turns integers (1–3999) into numerals and parses numerals back to numbers, both directions. It also validates well-formedness, so non-standard input like IIII or VV is rejected rather than silently accepted.
Everything runs entirely in your browser — nothing you type is uploaded, and it works completely offline.
Features
- Convert any integer from 1 to 3999 into a standard Roman numeral
- Parse Roman numerals back to integers, case-insensitively
- Validates well-formedness — rejects malformed forms like IIII or VV
- Fully offline; your input never leaves the device
How to use
- Paste a number or a Roman numeral into the input pane.
- Choose "To Roman" to convert a number, or "To Number" to parse a numeral.
- Copy the result from the output pane — or clear and start again.
Frequently asked questions
What range of numbers is supported?
The standard range is 1 to 3999. Classical Roman numerals have no symbol for zero and no compact way to write 4000 or more without overlines, so most converters stop at MMMCMXCIX (3999).
Why is 4 written IV and not IIII?
Standard Roman numerals use subtractive notation: a smaller symbol before a larger one means "subtract", so IV is 5 − 1 = 4 and IX is 10 − 1 = 9. The form IIII appears on some clock faces by tradition, but it is non-standard, so this tool rejects it.
Is the parser case-sensitive?
No. Input is uppercased before parsing, so "mcmxciv" and "MCMXCIV" both convert to 1994. Surrounding whitespace is ignored too.
Does my data get sent anywhere?
No. All conversion happens locally in your browser. Your input never leaves your device, and the tool works with no network connection.
Related tools
Everything runs locally in your browser — your input is never uploaded.