Roman ↔ Arabic Numerals Converter

Roman ↔ Arabic Numerals Converter – convert Roman numerals online

🔢 Free online converter instantly converts Roman numerals to Arabic numbers and back. Supports strict validation and normalization (e.g., VIIII → IX). Range: 1–3999 (I–MMMCMXCIX).

What this converter does

• Converts Roman numerals to Arabic and back
• Validates input and highlights errors
• “Normalize” button to enforce canonical notation

How to use

1️⃣ Enter a Roman numeral (e.g., MCMXCIV) — you’ll get 1994
2️⃣ Or enter an Arabic number (2025) — you’ll get MMXXV
3️⃣ Click “Normalize” to fix non-standard forms

Roman numeral rules (briefly)

• Allowed subtractive pairs: IV, IX, XL, XC, CD, CM
• V, L, D do not repeat; I, X, C, M no more than three in a row
• Only I V X L C D M are allowed; other symbols are invalid

Examples

4 → IV, 9 → IX, 58 → LVIII, 90 → XC, 944 → CMXLIV, 1994 → MCMXCIV, 2025 → MMXXV.

Why it’s useful

• Check dates and section numbering in documents/design
• Education: history of numerals and numeral systems
• Quick verification of Roman notation with normalization

FAQ

• What range is supported? 1–3999 — the classical limit of canonical notation.
• Why is 49 written as XLIX, not IL? IL isn’t an allowed pair; the correct form is XLIX.
• Can I convert zero, fractions, or negatives? No, only positive integers within the range.
• What is “normalization”? Automatic conversion to the canonical form (e.g., VIIII → IX).