Roman Numeral Converter

Convert a number into Roman numerals, or type Roman numerals to get the number back. Works both ways as you type, with proper subtractive notation (4 = IV, 9 = IX, 40 = XL, and so on). Handles 1 to 3999 — the standard range of classic Roman numerals.

How Roman numerals work

• Symbols: I = 1, V = 5, X = 10, L = 50, C = 100, D = 500, M = 1000.
• Add when a smaller or equal symbol follows (VI = 6), subtract when a smaller one comes first (IV = 4, IX = 9).
• A symbol repeats at most three times (III = 3); 4 is IV, not IIII.
• There's no zero and no standard way to write above 3999 with plain letters.

FAQ

How do I write a number in Roman numerals?

Combine the symbols I(1), V(5), X(10), L(50), C(100), D(500), M(1000), adding when a smaller symbol follows a larger one and subtracting when it precedes one. For example 2024 is MMXXIV.

What is the largest Roman numeral?

With standard letters the practical maximum is 3999 (MMMCMXCIX). Larger numbers historically used bars over letters to multiply by 1000, which this tool does not cover, so it supports 1–3999.

Why is 4 written as IV, not IIII?

Roman numerals use subtractive notation: a smaller symbol before a larger one is subtracted, so IV = 5 − 1 = 4. A symbol also repeats at most three times, which is why IIII is not standard — this tool rejects invalid forms.

Can it convert Roman numerals back to numbers?

Yes — type Roman numerals in the second field and it returns the number, validating that the input is a proper, canonical Roman numeral.

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