Numbers to Roman Numeral Converter

Workflow & Usage

1. Enter numbers or Roman numerals in the left textarea.
2. Use the Number / Roman toggle inside the input area to switch direction.
3. Optional controls:
   • Batch by newline — convert one value per line
   • Trim lines — ignore extra whitespace in batch mode
4. View results instantly on the right and copy with one click.

Invalid or non-canonical inputs are reported per line so the rest of the batch continues.

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Conversion Rules

Number

• Valid range: 1–3999
• Output uses canonical Roman notation

Example:

2025 → MMXXV

Roman

• Accepts uppercase or lowercase input
• Validates canonical structure
• Rejects invalid sequences

Example:

MMXXV → 2025

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Common Use Cases

• Learning Roman numerals
• Education and homework
• Historical references
• Game mechanics and puzzles
• Chapter or section numbering
• UI labels and outlines

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Tips & Best Practices

• Roman numerals are case-insensitive.
• Avoid non-standard forms like IIII or IC.
• Use batch mode for lists of years or identifiers.
• Values outside the supported range will return an error.

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How It Works

• Numbers are converted using a descending Roman value table
• Roman numerals are parsed left-to-right
• Subtractive pairs (IV, IX, XL, etc.) are handled correctly
• Decoded values are validated via round-trip conversion
• Each line is processed independently