Roman numerals today
Roman numerals were the number system of ancient Rome. They are still used on clock faces, for the names of kings and popes (Louis XIV), book chapters and prefaces, movie copyright years, Super Bowl numbers, building foundation stones, and in many school exams. This converter turns ordinary numbers into Roman numerals and back, and tells you if a numeral is written incorrectly.
How to use the converter
- Type a number between 1 and 3999 to see it in Roman numerals.
- Or type a Roman numeral to see its value. Upper or lower case both work.
- The breakdown shows which symbols make up the number.
The seven symbols
| I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|
| 1 | 5 | 10 | 50 | 100 | 500 | 1000 |
The rules
- Add values written from largest to smallest: VIII = 5 + 1 + 1 + 1 = 8.
- Subtract when a smaller symbol comes before a larger one: IV = 4, IX = 9, XL = 40, XC = 90, CD = 400, CM = 900. Only I, X and C are used this way, and only before the next two larger symbols.
- Repeat a symbol at most three times: III = 3, but 4 is IV, not IIII. (Some clock faces use IIII for decoration.)
- V, L and D are never repeated and never subtracted.
Worked example: 2026
Break the number into thousands, hundreds, tens and ones: 2000 + 20 + 6. Then 2000 = MM, 20 = XX and 6 = VI, so 2026 = MMXXVI. For 1994: 1000 = M, 900 = CM, 90 = XC, 4 = IV, giving MCMXCIV.
Frequently asked questions
Why does the converter stop at 3999?
4000 would need MMMM, which breaks the three-repeat rule. Romans wrote larger numbers with a bar over the symbol to multiply it by 1,000, but there is no standard way to type that.
Is there a Roman numeral for zero?
No. The Romans had no symbol for zero. The concept of zero as a number came from Indian mathematicians.
Why is IL wrong for 49?
I can only be subtracted from V and X. 49 is 40 + 9 = XL + IX = XLIX.