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Roman Numeral Converter

Free Roman numeral converter: convert any number from 1 to 3999 to Roman numerals, or convert Roman numerals back to numbers.

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A LITTLE CONTEXT · 5 MIN READHow Roman Numerals Work
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How roman numeral converter works

Roman numerals use seven symbols: I (1), V (5), X (10), L (50), C (100), D (500), and M (1000). Numbers are formed by combining these symbols, usually from largest to smallest. When a smaller symbol precedes a larger one, it is subtracted (e.g., IV = 4, IX = 9).

This converter handles both directions. To convert a number to Roman numerals, it repeatedly subtracts the largest possible symbol value. To convert Roman numerals to a number, it scans the symbols left to right, adding or subtracting values based on the subtractive notation rule.

The standard Roman numeral system represents numbers from 1 to 3999. Numbers outside this range cannot be represented in standard Roman numerals. The converter validates input and rejects invalid combinations.

Frequently asked questions

What is the largest number in Roman numerals?
The standard Roman numeral system represents numbers from 1 to 3999. The number 3999 is MMMCMXCIX. Larger numbers require special notation that is not part of the standard system.
How do I write 4 in Roman numerals?
4 is written as IV. The subtractive principle means a smaller symbol before a larger one is subtracted, so I (1) before V (5) gives 4. This is preferred over IIII.
How do I write 99 in Roman numerals?
99 is XCIX. XC means 90 (100 minus 10), and IX means 9 (10 minus 1). Combining them gives 99.
Does it handle invalid Roman numerals?
Only standard Roman numeral characters (I, V, X, L, C, D, M) are accepted. Non-standard spellings such as IIII, VV or IC parse but are flagged as non-canonical, and the proper subtractive form (IV, X, XCIX) is shown. Values beyond the classical 3999 limit are labelled as MMMM-style notation.

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