Roman Numeral Converter

Standard Roman numerals only go up to MMMCMXCIX (3999). Values above need the vinculum (an overline meaning ×1000), which isn't part of the basic system.

Roman numerals have no symbol for zero — they're a non-positional system.

It enforces canonical form. IIII is not valid (use IV); VV isn't valid (use X). Each numeral has exactly one canonical Roman spelling.

Yes — both lowercase and uppercase work; the result is shown in uppercase by convention.

Subtraction is only allowed from the next two symbols up, and only using I, X or C. So 999 is CMXCIX, not IM. The converter re-encodes whatever you type and compares it with your input, which is why anything outside the canonical form is refused rather than quietly interpreted.

As MCMXCIX, the same canonical form this tool produces. What varies in the wild is styling rather than structure: older inscriptions often use IIII on clock faces instead of IV, a convention kept for visual balance rather than because it is a different number system.