Roman & Arabic Numeral Converter
Convert Roman numerals to Arabic numbers and vice versa, instantly. Supports values up to 3999.
這個工具是做什麼的
A bidirectional converter for Roman and Arabic numerals. Paste a Roman numeral (like MCMXCIV) to get the Arabic value (1994), or type an Arabic number (like 2026) to get the Roman form (MMXXVI).
Useful for students, writers, history enthusiasts, and anyone working with copyright dates, regnal numbers, or formal numbering.
使用方法
- Type either a Roman numeral or an Arabic number into the input field.
- The converted result appears instantly in the other field.
- Switch direction at any time — the tool detects which form you typed.
常見問題
Why is the maximum 3999?
Standard Roman numerals run from I (1) to MMMCMXCIX (3999). Larger values require non-standard notation (overlines or vinculum) which most contexts don't expect.
Does it accept lowercase Roman numerals?
Yes. Both 'mcmxciv' and 'MCMXCIV' convert correctly.
What about IIII vs IV?
The tool outputs the standard subtractive form (IV, IX, XL, XC, CD, CM). Non-standard forms like IIII (sometimes seen on clock faces) are accepted as input but normalized.
Does it support zero or negative numbers?
No. Roman numerals have no representation for zero or negatives, so the converter only handles 1–3999.