Roman Numerals
The converter turns numbers from 1 to 3999 into Roman numerals and back, breaks them down by place value and checks that they are written correctly.
The Roman numerals converter turns numbers from 1 to 3999 into Roman numerals and back, breaks the number down by place value and checks whether a Roman numeral is written correctly.
Roman numerals
| I | V | X | L | C | D | M |
|---|---|---|---|---|---|---|
| 1 | 5 | 10 | 50 | 100 | 500 | 1000 |
Rules for writing Roman numerals
- Numerals are written from largest to smallest and their values are added: XVI = 10 + 5 + 1 = 16.
- If a smaller numeral comes before a larger one, it is subtracted: IV = 5 − 1 = 4, XC = 100 − 10 = 90.
- Only I (before V and X), X (before L and C) and C (before D and M) can be subtracted.
- The same numeral repeats at most three times in a row: 3 = III, but 4 = IV, not IIII.
How to convert a number to Roman numerals
Split the number by place value and write each place separately:
Example. 1987 = 1000 + 900 + 80 + 7
1000 = M, 900 = CM, 80 = LXXX, 7 = VII
1987 = MCMLXXXVII
| Digit | Ones | Tens | Hundreds | Thousands |
|---|---|---|---|---|
| 1 | I | X | C | M |
| 2 | II | XX | CC | MM |
| 3 | III | XXX | CCC | MMM |
| 4 | IV | XL | CD | |
| 5 | V | L | D | |
| 6 | VI | LX | DC | |
| 7 | VII | LXX | DCC | |
| 8 | VIII | LXXX | DCCC | |
| 9 | IX | XC | CM |
How to convert Roman numerals to a number
Go from left to right: if a numeral is smaller than the next one, subtract it, otherwise add it.
Example. MCMXCIX = 1000 − 100 + 1000 − 10 + 100 − 1 + 10 = 1999
Roman numerals are used for centuries (the 21st century is the XXI century), book chapters, monarchs (Elizabeth II), movie sequels and clock faces.