BYTETOOLS

Roman Numeral Converter

Convert numbers to Roman numerals and Roman numerals back to numbers (1–3999). Free two-way Roman numeral converter with input validation.

Roman numeral

MMXXIV

  • Two-way conversion between numbers and Roman numerals
  • Covers the full valid range 1 to 3999
  • Standard subtractive notation (IV, IX, XL, XC…)
  • Rejects invalid or malformed numerals
  • One-click copy of the result
  • Runs entirely in your browser

How to use the Roman Numeral Converter

  1. 1

    Choose a direction: Number → Roman or Roman → Number.

  2. 2

    Type a number from 1 to 3999, or a Roman numeral.

  3. 3

    Read the converted value instantly below the input.

  4. 4

    Copy the result to your clipboard with one click.

About the Roman Numeral Converter

The ByteTools Roman Numeral Converter translates any whole number from 1 to 3999 into Roman numerals, and converts Roman numerals back into ordinary numbers. It is handy for reading clock faces, book chapters, movie sequels, monument dates and Super Bowl numbering.

The converter follows standard subtractive notation — 4 is IV, 9 is IX, 40 is XL — and validates your input, so a malformed numeral like IIII or VX is rejected rather than silently mis-read. Switch direction with a single click.

All conversion happens locally in your browser with JavaScript. Nothing is uploaded or stored, so you can convert freely and copy the result to your clipboard in one tap.

Frequently asked questions

What is the largest number in Roman numerals?

Using standard notation, the largest value is 3999, written MMMCMXCIX. There is no standard symbol for zero or for numbers above 3999 without special overline notation, so this converter covers the everyday 1–3999 range.

How do you write 4 and 9 in Roman numerals?

They use subtractive notation: 4 is IV (one before five) and 9 is IX (one before ten). The same pattern gives 40 as XL, 90 as XC, 400 as CD and 900 as CM. Writing 4 as IIII is considered non-standard.

Why is my Roman numeral rejected?

The converter validates each numeral by converting it back and comparing. Entries that break the rules — repeating a symbol too many times, or an invalid order like IL — do not round-trip cleanly, so they are flagged as invalid.

What are the basic Roman numeral symbols?

The seven symbols are I (1), V (5), X (10), L (50), C (100), D (500) and M (1000). Every number from 1 to 3999 is built by combining these using additive and subtractive rules.

Is there a Roman numeral for zero?

No. The Roman system has no symbol for zero, which is why conversions start at 1. Medieval scholars sometimes used the word 'nulla' for nothing, but it was never part of the numeral notation.

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