Decimal to Roman Numeral Converter [2025]

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Convert decimal numbers (integers from 1 to 3999) to their Roman numeral equivalents.

✓ Handles numbers 1-3999

Decimal Input

Roman Numeral Output

Key Features

  • Convert decimal numbers to Roman numerals.
  • Supports numbers in the range 1 to 3999 (inclusive).
  • Provides clear error messages for invalid input (non-numeric or out-of-range).
  • Example data for quick testing.
  • Copy functionality for the converted Roman numeral output.

Common Use Cases

Education

  • • Learning Roman numerals
  • • History classes
  • • Number system conversions

General Use

  • • Converting dates
  • • Numbering outlines
  • • Understanding Roman numerals in context

Design

  • • Creating classic-looking clocks
  • • Designing with Roman numerals
  • • Adding a historical touch to designs

Frequently Asked Questions

What is the range of numbers supported?

This converter supports decimal numbers from 1 to 3999, which is the standard range for Roman numerals.

What are the basic Roman numeral symbols?

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

How are larger numbers represented?

Roman numerals are formed by combining symbols and adding their values. For example, II = 2, VI = 6. A smaller value placed *before* a larger value indicates subtraction (e.g., IV = 4, IX = 9).

Is my data secure?

All processing is done client-side in your browser. No data is sent to a server.

Technical Details

Conversion Algorithm

The conversion uses a greedy algorithm, iterating through Roman numeral values from largest to smallest and subtracting the corresponding decimal value until the input number reaches zero.

Subtraction Rule:

  • • I can be placed before V and X (IV = 4, IX = 9).
  • • X can be placed before L and C (XL = 40, XC = 90).
  • • C can be placed before D and M (CD = 400, CM = 900).

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