Roman Numeral Converter
Type a number or a Roman numeral into either box — the other one fills in automatically. Supports 1 through 3,999,999, using the traditional overline convention for anything past 3,999.
Try a few examples
Roman numeral symbols
The seven base symbols, and the six subtractive combinations built from them.
| Symbol | Value |
|---|---|
| I | 1 |
| V | 5 |
| X | 10 |
| L | 50 |
| C | 100 |
| D | 500 |
| M | 1,000 |
| IV | 4 (5 − 1) |
| IX | 9 (10 − 1) |
| XL | 40 (50 − 10) |
| XC | 90 (100 − 10) |
| CD | 400 (500 − 100) |
| CM | 900 (1,000 − 100) |
The subtractive rule, and why there's no Roman numeral for zero
Roman numerals build a number by lining up symbols and adding them: III is 1+1+1 = 3. But when a smaller symbol comes before a larger one, it's subtracted instead of added — IV is "one before five," or 4, rather than 1+5=6. This subtractive notation exists purely to avoid writing the same symbol four times in a row: without it, 4 would be IIII and 9 would be VIIII. Interestingly, the Romans themselves weren't fully consistent about this — genuine Roman inscriptions sometimes used IIII for 4, and this converter's strict, standard form (which most modern style guides and this page follow) reflects a convention that solidified more firmly in medieval and modern usage than it was in Rome itself. It's also why some clock faces still show IIII at the 4 rather than IV — both are historically legitimate.
There is, genuinely, no symbol for zero. The Roman numeral system was built for counting and recording quantities, not for the kind of positional arithmetic zero enables (the concept reached Europe centuries later, via Indian and then Arabic mathematics) — so a Roman numeral can represent "how many," but never "none."
Roman numerals haven't disappeared from daily life: clock faces, Super Bowl numbering, movie and TV copyright years, monarch and pope regnal numbers (Elizabeth II, Louis XIV), and the lowercase preliminary pages of books (i, ii, iii…) all still use them.
Beyond 3,999: the overline convention this converter supports
Standard Roman numerals only go up to 3,999 — M can only repeat 3 times before you'd need a fourth, and there's no standard symbol above M. But there's a traditional workaround, and this converter supports it: draw a horizontal line (a vinculum, or overline) over a numeral, and it's multiplied by 1,000. So an overlined L means 50 × 1,000 = 50,000, and an overlined CM means 900 × 1,000 = 900,000 — extending the practical range all the way to 3,999,999.
Type a number bigger than 3,999 into the Number box and the Roman Numeral box will show the overline automatically, rendered right over the relevant letters. If you'd rather type a large Roman numeral by hand, use a leading underscore before each letter that needs the overline (matching the convention used by other Roman numeral converters) — _C_M gets you the same 900,000 as a true overlined CM, just typed with an ordinary keyboard.