Roman Numeral Converter
Type an Arabic number to see its Roman form, or type Roman letters to see the number. Both fields stay in sync as you type, only valid canonical Roman numerals are accepted, and you can copy either side with one click.
Standard Roman numerals support 1 – 3999.
How to use
- Type a number from 1 to 3999 in the left field.
- Or type Roman letters (M, D, C, L, X, V, I) on the right.
- The other field updates automatically.
- Use the copy button next to either value.
Frequently asked questions
- Why is the range limited to 3999?
- 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.
- Is there a zero?
- Roman numerals have no symbol for zero — they're a non-positional system.
- Why is my input rejected?
- It enforces canonical form. IIII is not valid (use IV); VV isn't valid (use X). Each numeral has exactly one canonical Roman spelling.
- Are lowercase letters accepted?
- Yes — both lowercase and uppercase work; the result is shown in uppercase by convention.
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