How it works
Numbers are written from the largest value down. Each place (thousands, hundreds, tens, ones) becomes its own group: 1994 is 1000 + 900 + 90 + 4, which is M + CM + XC + IV = MCMXCIV.
Numerals are read the other way: add each letter, but subtract it when a larger letter follows. The result is then checked against the standard spelling, so non-standard forms such as IIII or IC are flagged with the correct version.
The seven symbols
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1000 |
The rules
- A repeated letter repeats its value: III = 3, XX = 20. No letter is used more than three times in a row.
- A smaller letter after a larger one adds to it: VI = 6, LX = 60.
- A smaller letter before a larger one subtracts: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. Only I, X and C are subtracted, and only from the next two larger letters.
- Standard numerals stop at 3999 (MMMCMXCIX). Larger values historically used a bar over a letter to mean ×1000.
Tips
- Clock faces often show 4 as IIII. That is a design tradition; the standard form is IV.
- Years in film credits and on buildings are easy to read in groups: MCMLXXXIV = M CM LXXX IV = 1984.
- There is no Roman numeral for zero or negative numbers.
Standards and sources
- GPO Style Manual, Chapter 12 Numerals, rule 12.29 Roman numerals · U.S. Government Publishing Office
- Number Forms chart (U+2150–U+218F), Roman numeral characters · Unicode Consortium
Last reviewed October 17, 2026
Frequently asked questions
How do you write 2026 in Roman numerals?
MMXXVI: MM = 2000, XX = 20 and VI = 6.
Why is the limit 3999?
The standard system has no symbol above M (1000) and does not repeat a letter more than three times, so MMMCMXCIX (3999) is the largest standard numeral.
Is IIII wrong?
It is not the standard form. IIII appears on many clock faces by tradition, but the standard way to write 4 is IV. The converter reads IIII as 4 and shows the standard spelling.
Can I enter lowercase letters?
Yes. mcmxciv works the same as MCMXCIV, and single-character Unicode numerals such as Ⅻ are converted as well.