Roman Numeral Converter — Roman numerals use seven symbols (I, V, X, L, C, D, M) to represent numbers from 1 to 3,999. They were used throughout the Roman Empire and remain common in clock faces, monarchs (Henry VIII), movie sequels (Rocky II), and Super Bowl branding.
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Roman Numeral Converterとは？
Roman numerals use seven symbols (I, V, X, L, C, D, M) to represent numbers from 1 to 3,999. They were used throughout the Roman Empire and remain common in clock faces, monarchs (Henry VIII), movie sequels (Rocky II), and Super Bowl branding.
Enter a number to get its Roman form, or paste a Roman numeral to decode it back to an integer. Bidirectional conversion with input validation — invalid Roman forms are rejected with a clear error.
使い方
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Type a number
Any integer from 1 to 3,999.
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Or type a Roman numeral
Lowercase works too — it is normalized to uppercase.
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Read the result
The other side updates live as you type.
使用例
1994 in Roman numerals
A classic year used in many textbooks.
結果： MCMXCIV
Decode MCMLXXXIV
1984 in canonical Roman form.
結果： 1984
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Last reviewed: 2026-09-25