Convert a number to Roman numerals, or a Roman numeral to a regular number. Works for all numbers between 1 and 3999.
Roman numerals are built from seven base symbols: I (1), V (5), X (10), L (50), C (100), D (500) and M (1000). Numbers are formed by placing symbols after each other and summing the values — this is called additive notation, as in VI = 5 + 1 = 6.
When a symbol of lower value comes before a symbol of higher value, it's subtracted instead of added — this is called subtractive notation. That's why 4 is written "IV" (one less than five) instead of "IIII".
Modern use of Roman numerals is usually limited to numbers between 1 and 3999, since there's no standard single symbol for numbers from 5000 upward.
The Romans used subtractive notation to make numbers shorter: when a symbol of lower value comes before one of higher value, it's subtracted. IV therefore means 5 − 1 = 4, instead of repeating the symbol I four times.
This calculator supports numbers up to 3999 (MMMCMXCIX). There's no standard single symbol for 5000 or higher in the classical Roman numeral system.
Roman numerals are still used for things like clock faces, chapter numbering in books, movie titles and sequel numbers (like Super Bowl LVIII), and the names of kings and popes (like Louis XIV).