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Convert between integers and Roman numerals — supports 1 to 3999 with validation.
Quick reference
Every tool runs entirely in your browser. Nothing you type is uploaded, stored, or logged on our servers.
The Roman Numeral Converter converts integers between 1 and 3999 to their Roman numeral equivalents, and validates Roman numeral strings back to integers. Invalid or non-canonical inputs (e.g. IIII instead of IV) are rejected with a clear error message.
Click any entry in the quick reference table to load it instantly. Use Swap to flip between integer and Roman modes without retyping.
It converts Arabic numbers into Roman numerals and Roman numerals back into numbers, following standard notation rules.
No. Conversion happens client-side in your browser, so nothing you enter is uploaded.
Standard Roman numerals cover 1 to 3999 using the symbols I, V, X, L, C, D, and M, which is the range this converter handles.
Smaller values placed before larger ones are subtracted, so IV is 4 and IX is 9, which the converter applies automatically.
The Roman system has no symbol for zero, so conversion starts at 1. Non-positive or out-of-range inputs cannot be represented.