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Roman Numeral ConverterConvert between Arabic numbers and Roman numerals.

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Roman Numeral Converter

Convert between Arabic numbers and Roman numerals.

How to Use
1

Choose Direction

Select Number → Roman or Roman → Number.

2

Enter Value

Enter numbers or Roman numerals, one per line.

3

Copy Result

Copy the converted values.

What Is Roman Numeral Converter?

The Roman Numeral Converter converts between Arabic numbers (1-3999) and Roman numerals (I-MMMCMXCIX). In Number to Roman mode, enter decimal numbers to get their Roman numeral representation. In Roman to Number mode, enter Roman numerals to get their decimal equivalents. The converter supports standard subtractive notation (IV=4, IX=9, XL=40, XC=90, CD=400, CM=900) and processes multiple values at once (one per line).

Why Use Our Roman Numeral Converter?

  • Bidirectional conversion between Arabic and Roman numerals
  • Supports standard subtractive notation
  • Process multiple values at once
  • Useful for academic, historical, and decorative purposes

Common Use Cases

Education

Learn and verify Roman numeral conversions.

Document Formatting

Convert page numbers, chapters, or section numbers to Roman numerals.

Historical Research

Convert Roman numeral dates and references.

Design

Generate Roman numerals for clock faces, monuments, or decorative text.

Technical Guide

The converter uses a greedy algorithm for number to Roman conversion. A sorted table of value-symbol pairs (from 1000/M down to 1/I, including subtractive combinations like 900/CM, 400/CD, 90/XC, 40/XL, 9/IX, 4/IV) is iterated. For each pair, while the remaining number is greater than or equal to the value, the symbol is appended and the value subtracted. For Roman to number conversion, the string is scanned left to right. Each character's value is looked up. If a character's value is less than the next character's value, it is subtracted (subtractive notation); otherwise, it is added.

Tips & Best Practices

  • 1
    Valid range is 1 to 3999 (I to MMMCMXCIX)
  • 2
    Enter one value per line to convert multiple values
  • 3
    Roman to Number accepts both upper and lowercase input
  • 4
    Subtractive notation is used (IV instead of IIII)

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Frequently Asked Questions

QWhat is the maximum number?
3999 (MMMCMXCIX). Standard Roman numerals do not have a symbol for 5000 or above.
QWhat is subtractive notation?
Placing a smaller value before a larger one indicates subtraction: IV=4, IX=9, XL=40, XC=90, CD=400, CM=900.
QIs the input case-sensitive?
No, Roman numerals can be entered in uppercase or lowercase.
QWhat about zero?
Roman numerals have no symbol for zero. Only values 1-3999 are supported.
QCan I convert negative numbers?
No, Roman numerals only represent positive integers from 1 to 3999.

About Roman Numeral Converter

Roman Numeral Converter is a free online tool from FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration required. No ads. Just fast, reliable tools.