Roman Numerals
Convert decimal numbers to Roman numerals and vice versa. Supports values from 1 to 3,999,999 with vinculum notation. Instant result — use now.
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Roman Numeral Converter — Free Online Tool
The Roman Numeral Converter from facilita.tools lets you convert between decimal numbers and Roman numerals instantly — from 1 to 3,999,999. It supports the vinculum notation (overline) for values above 3,999, a feature rarely found in online converters. The tool offers two modes: decimal-to-Roman and Roman-to-decimal, each with a clear step-by-step breakdown showing how the conversion works. Roman numerals use seven symbols (I, V, X, L, C, D, M) combined with subtractive rules — for example, IV = 4, IX = 9, XL = 40, and XC = 90. For numbers above 3,999, the vinculum system multiplies a symbol by 1,000 by adding an overline: V̅ = 5,000, X̅ = 10,000, M̅ = 1,000,000. This converter is perfect for students studying history and mathematics, professionals working with legal or academic references, clock and watch enthusiasts, and anyone curious about numbering systems. Common uses include converting years (e.g., 2024 = MMXXIV), chapter and volume numbering, Super Bowl editions, and outlines. The converter also handles invalid input gracefully, alerting you with clear error messages when a value is out of range or contains unrecognized characters. All processing runs locally in your browser — no server communication, no registration, Works on any device with a modern browser.
Frequently Asked Questions
What is the maximum number supported?
The converter handles numbers from 1 to 3,999,999 using the vinculum system (overline notation) for values above 3,999. For example, 5,000 is represented as V̅ (V with overline).
What are subtractive Roman numeral rules?
In subtractive notation, a smaller symbol placed before a larger one means subtraction: IV = 4 (5 − 1), IX = 9 (10 − 1), XL = 40 (50 − 10), XC = 90 (100 − 10), CD = 400, CM = 900. This avoids repeating a symbol more than three times.
Where are Roman numerals used today?
Roman numerals are still commonly used for: centuries (XXI = 21st century), monarchs and popes (Elizabeth II, John Paul II), Super Bowl editions (Super Bowl LVIII), clock faces, book chapters, and legal documents. They are also standard in movie credits and building cornerstones.