Roman Numeral Converter (Number ↔ Roman)
Convert a number (1–3999) to Roman numerals, or decode a Roman numeral to a number.
🔒 Private by design. This tool runs entirely in your browser — the values you enter never leave your device.
Turn an ordinary number into Roman numerals using standard subtractive notation (like IV for 4 and XL for 40) — or switch direction to decode a Roman numeral back into a regular number. Great for dates, chapter numbers, clock faces and copyright years.
Formula / method
Examples
MMXXVI
XLIX
MMXXIV
2026
The seven basic symbols
Roman numerals are built from seven letters: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500, and M is 1000. When symbols are arranged from largest to smallest, you simply add them, so MDCLXVI reads as 1000 + 500 + 100 + 50 + 10 + 5 + 1 = 1666.
Subtractive notation and the 3999 limit
To avoid four repeated symbols, a smaller value placed before a larger one is subtracted: IV is 4, IX is 9, XL is 40, XC is 90, CD is 400, and CM is 900. There is no symbol for zero and no way to write negatives or fractions.
Standard Roman numerals stop at 3999 (MMMCMXCIX) because 4000 and above traditionally require a bar over a letter to multiply it by 1000, which plain text cannot show. That is why this tool accepts 1 to 3999.
Where it's used
- Writing a copyright year in film and television credits, such as MMXXVI
- Numbering book chapters, prefaces or outline sections
- Reading and setting clock and watch faces
- Naming monarchs, popes and movie sequels, like Henry VIII or Rocky IV
- Marking Super Bowl numbers and Olympiads
Real-world examples
- 2026 becomes MMXXVI
- 4 is written IV and 49 becomes XLIX using subtractive notation
- 1666, which uses one of each main symbol, is MDCLXVI
A bit of history
Roman numerals originated in ancient Rome and stayed the standard way of writing numbers across Europe for centuries, only gradually giving way to Hindu-Arabic numerals in the late Middle Ages.
Did you know?
Traditional clock and watch faces almost always show four o'clock as IIII rather than the subtractive IV; the reason is debated, with explanations ranging from better visual balance against the VIII opposite it to easier casting of the numerals.
FAQ
Why only up to 3,999?
Standard Roman numerals have no single symbol above M (1,000), so 3,999 (MMMCMXCIX) is the usual maximum without special overline notation.
How do I convert Roman numerals back to numbers?
Switch the direction to Roman → Number and type a numeral using I, V, X, L, C, D and M. The tool applies standard subtractive rules to compute its value.