Roman Numeral Converter

About the Roman Numeral Converter

The Roman Numeral Converter translates between Roman numerals and decimal (Arabic) numbers. Enter a decimal number (1–3,999) to get its Roman representation, or enter Roman numerals to get the decimal value.

Roman numerals use seven symbols: I (1), V (5), X (10), L (50), C (100), D (500), M (1000). Subtractive notation places a smaller symbol before a larger one to represent subtraction (IV = 4, IX = 9, XL = 40, etc.).

Roman numerals still appear in clock faces, book chapters, movie sequels, Super Bowl numbers, and formal outlines. This converter handles all standard Roman numeral values and validates input.

When This Page Helps

Roman numeral conversion involves memorizing rules and subtractive patterns. This converter works in both directions and validates the input.

How to Use the Inputs

1. Enter a decimal number (1–3,999) to convert to Roman.
2. Or enter Roman numerals (e.g. MCMXCIV) to convert to decimal.
3. The converter auto-detects input type.
4. View both representations simultaneously.
5. Use for dates, outlines, or general reference.

Example Calculation

Tips & Best Practices

• Subtractive pairs: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.
• A symbol is never repeated more than three times in a row.
• There is no Roman numeral for zero.
• Standard Roman numerals go up to 3,999 (MMMCMXCIX).
• Modern years are often written in Roman numerals on buildings, title cards, and commemorative displays.
• Super Bowl numbers use Roman numerals (e.g. Super Bowl LVIII = 58).

History of Roman Numerals

Roman numerals originated in ancient Rome around 500 BCE. They were the dominant Western numeral system for over a thousand years until Arabic numerals (with zero and place value) gained popularity in the Middle Ages.

Subtractive Notation Rules

Only I, X, and C can be used subtractively, and only before the next two larger symbols: I before V and X, X before L and C, C before D and M.

Beyond 3,999

Historically, a bar (vinculum) over a numeral multiplied its value by 1,000. So V̄ = 5,000 and M̄ = 1,000,000. Some modern systems use parentheses instead.

Frequently Asked Questions

• How do Roman numerals work?

  Roman numerals use additive and subtractive notation. Symbols are generally written largest to smallest (left to right) and added together. A smaller symbol before a larger one is subtracted.

• What is subtractive notation?

  Placing a smaller symbol before a larger one indicates subtraction: IV = 5−1 = 4, IX = 10−1 = 9. Only I, X, and C can be used subtractively.

• Why is there no zero in Roman numerals?

  Roman numerals were developed before the concept of zero was introduced. The system is additive/subtractive and does not need a placeholder digit.

• What is the largest Roman numeral?

  Using standard notation, MMMCMXCIX = 3,999. To represent larger numbers historically, a bar (vinculum) was placed over a numeral to multiply by 1,000.

• How do you write years in Roman numerals?

  Break the year into place values and convert each part, then combine them. For example, 1994 = 1000 + 900 + 90 + 4 = MCMXCIV. Years are commonly seen on building cornerstones, movie credits, and clock faces.

• Are Roman numerals still used today?

  Yes. They appear on clocks, in outlines, for numbering monarchs (Henry VIII), Super Bowl edition numbers, copyright years in film credits, and book chapter headings.