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Updated 2026 · By ToolFern

Roman Numeral Converter

Convert both ways and live: type a number (1-3999) to get its Roman numeral, or type a Roman numeral to get the number. It uses proper subtractive notation (IV, IX, XL, XC, CD, CM) and validates your input as you type.

Roman
Number

Quick examples:

Full date → Roman numerals

Popular for engravings, tattoos and anniversary gifts. Day, month and year each convert with the same rules used above.

Order
Date

Example: December 25, 2024 becomes XII.XXV.MMXXIV in Month.Day.Year order, or XXV.XII.MMXXIV in Day.Month.Year order. Roman numerals only cover the years 1 to 3999.

How to use the Roman numeral converter

  1. Number to Roman: type a whole number from 1 to 3999 in the left box. The Roman numeral appears instantly below it.
  2. Roman to number: type a Roman numeral (such as MMXXVI) in the right box. Letters are auto-capitalised, and the decimal value appears below.
  3. Tap an example chip to fill the number box with a classic tricky value like 4, 444 or 1994.
  4. Copy either result with the button beside it.

How Roman numerals work

Roman numerals combine seven letters, I (1), V (5), X (10), L (50), C (100), D (500) and M (1000). You read them left to right, adding each symbol's value. So MMXXVI is 1000 + 1000 + 10 + 10 + 5 + 1 = 2026. When a smaller symbol sits directly before a larger one, it is subtracted instead, that is the modern standard known as subtractive notation.

There are exactly six subtractive pairs: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). They exist so that no symbol repeats more than three times in a row, which is why 4 is IV rather than IIII, and 90 is XC rather than LXXXX. This tool always outputs the canonical form and only accepts well-formed numerals, so you can trust the result for dates, book chapters, clock faces, movie sequels and monument inscriptions.

Frequently asked questions

What is the largest value, 3999?

Without overline (vinculum) notation the largest standard numeral is MMMCMXCIX = 3999, because you can show at most three Ms. This converter sticks to that classic, unambiguous range.

Does it accept lowercase letters?

Yes. Type mcmxciv or MCMXCIV, the Roman box upper-cases your input automatically before converting.

Why does IIII or IC show an error?

Those are not valid standard numerals. Four Is in a row and skip-a-step subtractions like IC break the rules, so the tool rejects them rather than guessing what you meant.

Why can't I convert 0 or negative numbers?

The Roman system has no symbol for zero and no concept of negative quantities, so valid numerals start at 1. Inputs of 0, blanks or negatives are flagged with an error instead of a misleading result.

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