Roman Numeral Converter — Free Online Tool
Convert between numbers and Roman numerals (1–3999) in both directions.
Number → Roman
Roman → Number
About Roman Numeral Converter
The Roman Numeral Converter translates ordinary numbers into Roman numerals and converts Roman numerals back into numbers, covering the standard range of one to three thousand nine hundred ninety-nine. It is helpful for clock faces, book chapters, movie release years, and history homework.
The tool validates input in both directions, rejecting numbers outside the supported range and checking that a Roman numeral follows correct subtractive notation. That means it confirms a numeral is genuinely valid rather than just made of allowed letters.
How to Use Roman Numeral Converter
- Enter a number from 1 to 3999 and click Convert to get the Roman numeral.
- Or type a Roman numeral into the second box.
- Click Convert to turn the numeral back into a number.
- Read the result in the output field below each section.
Key Features
Two-way conversion between numbers and Roman numerals
Supports the full 1 to 3999 range
Validates correct subtractive notation
Clear separate sections for each direction
Instant results with no page reload
Frequently Asked Questions
Why is the range limited to 3999?
Standard Roman numerals use the letters up to M for one thousand, so without special overline notation the largest cleanly written value is 3999.
How does it know a numeral is valid?
After parsing, the tool converts the number back to a numeral and compares it to your input, which catches incorrectly ordered or repeated letters.
Which letters are allowed?
Only the seven Roman numeral letters I, V, X, L, C, D, and M are accepted, in upper or lower case.
Can it convert zero or negative numbers?
No. Roman numerals have no symbol for zero or negative values, so the tool only accepts numbers from 1 to 3999.