Roman Numeral Converter

Convert numbers to Roman numerals or Roman numerals to numbers instantly. Bidirectional, validates input, supports 1 to 3999, and shows the conversion breakdown.

I
1
V
5
X
10
L
50
C
100
D
500
M
1000

Enter a number between 1 and 3999 to see its Roman numeral form, or type a Roman numeral to see the decimal value. The converter works in both directions with instant results and input validation.

When to Use the Roman Numeral Converter

Use the Roman numeral converter for academic work, copyright dates, clock face references, outline numbering, Super Bowl numbers, or any time you need to convert between Arabic and Roman number systems.

Tips

  • The year 2024 in Roman numerals is MMXXIV — useful for copyright notices.
  • Remember the subtractive pairs: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900).
  • No Roman numeral symbol repeats more than three times in a row in valid notation.
  • Roman numerals are always read left to right, with larger values before smaller values except in subtractive cases.

Frequently Asked Questions

What numbers can be converted to Roman numerals? ▾

Standard Roman numerals represent 1 to 3999. There is no Roman numeral for zero, and numbers above 3999 require a bar notation (vinculum) that is rarely used in modern contexts.

How do Roman numerals work? ▾

Roman numerals use seven symbols: I (1), V (5), X (10), L (50), C (100), D (500), M (1000). Larger values go left; a smaller value before a larger means subtraction (IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900).

What is the subtractive rule? ▾

The subtractive rule allows a smaller numeral to be placed before a larger one to indicate subtraction. Only I, X, and C can be used subtractively, and only before the next two values in the sequence (I before V and X, X before L and C, C before D and M).

Why is 4 written as IV and not IIII? ▾

The subtractive form IV is the standard convention. While IIII appears on some clock faces (the watchmaker's four), the subtractive form has been standard since medieval times and is used in all formal contexts.

Can I convert Roman numerals to Arabic numbers? ▾

Yes. Type a Roman numeral like XIV and the converter instantly shows the Arabic number (14). It validates the input and flags invalid Roman numeral sequences.

Is the conversion bidirectional? ▾

Yes. Enter a number (1-3999) to get the Roman numeral, or enter a Roman numeral to get the number. The converter detects which direction you mean automatically.

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