Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers. Supports 1 to 3,999,999 with instant bidirectional conversion.
Quick reference
How to convert Roman numerals
Convert a number to Roman numerals or a numeral back to a number.
- 01
Choose the direction
Number to Roman or Roman to number. The swap button flips between them.
- 02
Type the value
Numbers from 1 to 3,999,999 can be converted to numerals. Numerals are read in upper or lower case and must be written the standard way, so XIV works but XIIII doesn't.
- 03
Copy the result
Or click one of the example numbers, such as 2024 or 3999, to see how they're written.
The seven symbols and the subtraction rule
Roman numerals add up symbols from largest to smallest: VIII is 5 + 1 + 1 + 1 = 8. To avoid four of the same symbol in a row, a smaller symbol placed before a larger one is subtracted, but only in six combinations.
| Symbol | Value | Subtractive pairs |
|---|---|---|
| I | 1 | IV = 4, IX = 9 |
| V | 5 | |
| X | 10 | XL = 40, XC = 90 |
| L | 50 | |
| C | 100 | CD = 400, CM = 900 |
| D | 500 | |
| M | 1,000 |
Worked example: 1994 is 1000 + 900 + 90 + 4, so M + CM + XC + IV = MCMXCIV. And 2026 is 2000 + 20 + 6, so MMXXVI. The subtraction is limited: I can only come before V and X, X before L and C, and C before D and M. That's why 99 is XCIX, not IC.
Numbers above 3,999
With the seven basic symbols the largest standard numeral is MMMCMXCIX, 3,999. For bigger numbers, a bar over a symbol, called a vinculum, multiplies it by 1,000: V̄ is 5,000 and M̄ is 1,000,000. The converter uses this to write numbers up to 3,999,999, so 5,000 comes out as V̄.
Reading works only for the standard range up to 3,999, since overlined characters are hard to type and rarely used. Input is also checked against the standard form: IIII, IC or VX add up to a number, but they aren't valid numerals, so they're rejected rather than quietly converted.
Numbers people look up most
These are the conversions that trip people up, with the subtractive pairs that make them tricky:
| Number | Roman numeral | How it's built |
|---|---|---|
| 4 | IV | 5 − 1 |
| 9 | IX | 10 − 1 |
| 14 | XIV | 10 + (5 − 1) |
| 40 | XL | 50 − 10 |
| 49 | XLIX | (50 − 10) + (10 − 1), not IL |
| 99 | XCIX | (100 − 10) + (10 − 1), not IC |
| 444 | CDXLIV | 400 + 40 + 4 |
| 1666 | MDCLXVI | Every symbol once, largest to smallest |
| 1999 | MCMXCIX | 1000 + 900 + 90 + 9 |
| 3888 | MMMDCCCLXXXVIII | The longest numeral below 4,000, at 15 symbols |
| 3999 | MMMCMXCIX | The largest standard numeral |
A quick way to build any numeral: split the number into thousands, hundreds, tens and units, write each part on its own, and join them. 2026 is 2000 (MM) + 20 (XX) + 6 (VI), so MMXXVI.
Where Roman numerals show up
Copyright years in film and TV credits
MCMXCIX on an old film means 1999. Paste it in to check the year.
Clock faces, book chapters and outlines
Write chapter or section numbers the classic way, from I to MMMCMXCIX.
Event names and dates
Super Bowl LX is 60, and a wedding date such as 14 February 2026 can be engraved as XIV · II · MMXXVI.