How to use
- Type a number from 1 to 3,999, or a Roman numeral such as MMXXVI.
- The converter works out which way to go and shows the answer.
- Check the place-value breakdown to see how each part is built.
If a numeral is not in standard form, such as IIII, you get the standard spelling and the reason.
How Roman numeral conversion works
Seven letters carry the values:
| Letter | Value | Letter | Value |
|---|---|---|---|
| I | 1 | C | 100 |
| V | 5 | D | 500 |
| X | 10 | M | 1,000 |
| L | 50 |
Standard form follows four rules:
- Write each place value on its own, largest first: thousands, hundreds, tens, ones.
- A letter can repeat up to three times: III is 3 and XXX is 30.
- Six pairs use subtraction: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900).
- V, L and D are never repeated.
Examples
- 2026: MM + XX + VI = MMXXVI
- 1984: M + CM + LXXX + IV = MCMLXXXIV
- 1999: M + CM + XC + IX = MCMXCIX, not MIM
- 3999: MMM + CM + XC + IX = MMMCMXCIX, the largest standard numeral
Roman numerals chart
| Number | Numeral | Number | Numeral |
|---|---|---|---|
| 1 | I | 20 | XX |
| 2 | II | 40 | XL |
| 3 | III | 50 | L |
| 4 | IV | 90 | XC |
| 5 | V | 100 | C |
| 6 | VI | 400 | CD |
| 7 | VII | 500 | D |
| 8 | VIII | 900 | CM |
| 9 | IX | 1,000 | M |
| 10 | X | 2,000 | MM |
| Year | Numeral |
|---|---|
| 2000 | MM |
| 2024 | MMXXIV |
| 2025 | MMXXV |
| 2026 | MMXXVI |
| 2027 | MMXXVII |
More detail: clocks, big numbers and older forms
- Clock faces often show IIII instead of IV. It is a long tradition, but this converter treats IIII as non-standard.
- Above 3,999, a bar over a letter (a vinculum) multiplied it by 1,000, so V with a bar meant 5,000. This converter sticks to standard form.
- Older tables are less strict. The US Government Publishing Office style manual lists IC for 99 and MCM or MDCCCC for 1900. Modern standard form writes 99 as XCIX.
Need to spell a number out instead? Try the number to words converter.