Roman numeral converter
Turn numbers into Roman numerals or read them back. Covers 1 to 3999 and rejects malformed numerals instead of guessing.
Input
Roman numeral
ConvertedType a number to see its Roman numeral.
Roman numerals combine seven letters — I, V, X, L, C, D, M — using addition and a subtractive rule (IV = 4, IX = 9). The standard system spans 1 to 3999; larger values historically used an overline to multiply by a thousand, which this tool doesn't cover.
- Range
- 1–3999
- Direction
- Both ways
Related tools
This Roman numeral converter works both ways. Type 2024 to get MMXXIV, or switch the direction and type MMXXIV to get 2024. It covers 1 to 3999 using standard subtractive notation (IV, IX, XL, and so on). A number outside that range, or a numeral that isn't in standard form like IIII or IC, gets an error message rather than a guess. Lowercase input works too.
How to use the Roman numeral converter
- Under Direction, choose Number → Roman or Roman → Number.
- Type a whole number from 1 to 3999, or a numeral such as XLII.
- The result updates as you type.
- Click the result, or Copy result, to copy it.
The subtractive rule explained
Roman numerals use seven letters: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Values normally run from largest to smallest and add up, but a smaller letter placed before a larger one is subtracted. Only six pairs work that way: IV (4), IX (9), XL (40), XC (90), CD (400), and CM (900). Anything else, like IC for 99 or VX for 5, isn't standard and gets rejected. 99 is XCIX.
Frequently asked questions
What is the largest number the Roman numeral converter handles?
3999, written MMMCMXCIX. Larger numbers were traditionally written with a bar over a numeral to multiply it by 1,000, and this tool doesn't support that.
Why is 4 written as IV and not IIII?
IV is the standard form: the I before the V means 5 minus 1. IIII does turn up, most famously on clock faces, but this converter follows the standard form and rejects it.
Is this converter two-way?
Yes. Pick the direction, then enter 2024 to get MMXXIV, or MMXXIV to get 2024.
What happens with invalid input?
You get an error message, never a wrong answer. Numbers outside 1 to 3999, letters other than M, D, C, L, X, V, and I, and badly formed numerals such as IIII or VV are all flagged.
Built and maintained by Bipul Kumar. Found a wrong number or a broken result? Tell me and I'll fix it.