Roman numerals still turn up on clock faces, film credits, book chapters, Super Bowls and the dates carved on buildings. Reading a long one is harder than it looks.
It works both ways and tells you when a numeral isn’t valid.
How to use the Roman Numeral Converter#
- Choose a direction. Number to Roman numeral, or the other way round.
- Enter the value. Use 1 to 3,999, or type the letters.
- Read the result. Invalid numerals are flagged.
The seven symbols#
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1,000 |
Symbols are written from largest to smallest and added together. When a smaller symbol comes before a larger one, it’s subtracted: IV is 4 and IX is 9. Only I, X and C are used this way, and only once.
A worked example#
Break the number into thousands, hundreds, tens and ones, and write each part. 1994 is 1000 + 900 + 90 + 4, which is M + CM + XC + IV, or MCMXCIV.
Why the limit is 3,999#
The standard system has no symbol for 5,000, so the largest number you can write without extra notation is MMMCMXCIX, which is 3,999. A bar over a numeral, which multiplies it by 1,000, is used in some contexts for larger numbers. To convert a whole date, try the Roman numeral date converter.
Common mistakes#
The rules are strict. A symbol can repeat at most three times in a row, so 4 is IV, not IIII, in standard use. Only I, X and C can be subtracted, and only from the next two larger symbols. That means 99 is XCIX, not IC, and 45 is XLV, not VL.
| Year | Roman numeral |
|---|---|
| 1999 | MCMXCIX |
| 2000 | MM |
| 2024 | MMXXIV |
| 2025 | MMXXV |
| 2026 | MMXXVI |
Counting the rules#
Roman numerals follow a few rules. A symbol repeated up to three times adds: III is 3, XXX is 30. A smaller symbol written before a larger one subtracts, but only in six pairs: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). The symbols V, L and D are never repeated or subtracted. Numbers are written from the largest to the smallest place value, so each digit is converted on its own.
For 1994, take 1000 (M), 900 (CM), 90 (XC) and 4 (IV): MCMXCIV. For 2027, take 2000 (MM), 20 (XX) and 7 (VII): MMXXVII. The longest numeral under 4,000 is 3888, which is MMMDCCCLXXXVIII, fifteen letters.
Where you still see them#
- Clock faces, where 4 is often written IIII, a tradition that goes back centuries and keeps the dial visually balanced.
- The Super Bowl, numbered in Roman numerals since the fifth game, so Super Bowl LX is the 60th.
- Monarchs and popes, such as Elizabeth II or Benedict XVI.
- Outlines and legal documents, chapters in books, film copyright years and the front matter of books.
Some of these use variants. If a clock says IIII, it is not wrong, it is a convention.
A short history, and no zero#
The system developed in ancient Rome and was used across Europe for more than a thousand years. It has no zero and is poor for arithmetic, which is why it was replaced by the Hindu-Arabic numerals we use today. Medieval scholars did use the word nulla for zero, but they had no symbol for it. Multiplying XIV by XXIII is painful, but 14 × 23 is straightforward, and that is the reason most mathematics moved to the new numbers.
| Number | Roman numeral | Number | Roman numeral |
|---|---|---|---|
| 4 | IV | 90 | XC |
| 9 | IX | 400 | CD |
| 14 | XIV | 1,000 | M |
| 40 | XL | 1,994 | MCMXCIV |
| 49 | XLIX | 2,027 | MMXXVII |
| 64 | LXIV | 3,999 | MMMCMXCIX |
A few handy checks#
If a numeral has more than three of the same letter in a row, it is wrong in standard notation, so IIII should be IV, and XXXX should be XL. The letters V, L and D appear at most once. Larger values always come first except in the six subtractive pairs. When you convert a year, do it digit by digit: 1,000s, 100s, 10s, then 1s. For the year 2024: MM, XX, IV, giving MMXXIV.
Frequently asked questions#
MMXXVI.
In the standard system, MMMCMXCIX, which is 3,999.
No. The system has no symbol for zero.
Standard modern usage is IV, though IIII appears on many clock faces.
Read from left to right and add the values, except when a smaller symbol comes before a larger one, in which case you subtract it. For MCMXCIV, M is 1000, CM is 900, XC is 90 and IV is 4, which gives 1994. The converter does both directions, from a number to a numeral and from a numeral to a number.