Roman Numerals Converter Free Online
Convert between Roman numerals and Arabic numbers (1–3999). Both directions supported with breakdown showing how the numeral is built from M, D, C, L, X, V, I.
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Roman Numerals Converter Features
Classical Standard
Subtractive notation: IV=4 (not IIII), IX=9, XL=40, XC=90, CD=400, CM=900. Used in ISO 8601 supplementary, copyright dates, monarchs, Super Bowl numbering.
Range 1-3999
Standard Roman numerals max out at 3999 (MMMCMXCIX). Larger numbers historically used a vinculum (bar over numeral × 1000), not supported here.
Bidirectional
Type a number → Roman numeral. Type a numeral → Arabic. Auto-detected and validated.
Live Conversion
Type any input, see all results instantly.
Breakdown View
See exactly how the numeral is constructed: M × 2 = 2000, X × 2 = 20, V × 1 = 5. Great for learning.
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Free vs Pro
| Feature | Free | Pro |
|---|---|---|
| Full roman numerals calculation | ||
| Live calculation | ||
| All-units result panel | ||
| Bulk batch calculation | — | |
| REST API access | — | |
| Save & share calculations | — |
Frequently Asked Questions
Subtractive notation: a smaller numeral before a larger one means subtract. IV = 5 − 1 = 4. IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. (Clock faces sometimes use IIII for visual symmetry, but IV is the formal standard.)
In standard notation, MMMCMXCIX = 3999. To go larger, the Romans used a vinculum (a bar over a letter to multiply by 1000): V̄ = 5000, M̄ = 1,000,000. We support 1-3999 only.
MMXXV = M (1000) + M (1000) + X (10) + X (10) + V (5) = 2025.
Tradition for copyright dates dates back to early film for both elegance and to obscure the production year (older films looked less dated). MCMXCV = 1995, MMXXIV = 2024, MMXXV = 2025.
No. Roman numerals have no representation of zero. The concept entered Europe via Arabic numerals (originally from India) around the 12th century. This calculator rejects 0 as invalid.