Roman numerals turn up in more places than you might expect: the faces of clocks and watches, the chapters of books, film and TV copyright dates, the names of kings and popes, the numbered editions of the Super Bowl, and the foundation stones of old buildings. If you need to write the year 2026 as MMXXVI, or read the date at the bottom of a building as MCMXCIV, this tool does both.
Put one entry on each line. By default it works out for itself whether each line is a number or a Roman numeral.
How the system works
Seven letters carry the values: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1,000. Numbers are built by adding the symbols from largest to smallest, so 2026 is M + M + X + X + V + I, or MMXXVI. Where a smaller symbol comes before a larger one, it is subtracted: IV is 4, IX is 9, XL is 40, XC is 90, CD is 400 and CM is 900. That is why 1994 is MCMXCIV: M (1000), CM (900), XC (90), IV (4).
No more than three of the same symbol may follow each other, which is why 4 is written IV in the standard form and not IIII. Clock faces are a well-known exception, many of them use IIII, and traditions differ over why. The converter follows the standard form and treats IIII as invalid.
The range, and why it stops at 3999
Standard Roman numerals have no symbol larger than M, so the biggest number you can write in the usual form is 3,999, MMMCMXCIX. Historically larger numbers were written with a bar over a letter to multiply it by a thousand, but that notation is not part of the common form and the converter does not support it. There is also no Roman numeral for zero, nor for negative numbers or fractions in the form used today. Inputs outside 1 to 3999 get a clear message.
Reading the options
“Detect automatically” looks at each line: digits become numerals, and letters from the set I, V, X, L, C, D and M become numbers. If you want to force one direction, such as when converting a list of numbers only, choose it. “Lowercase Roman numerals” writes the result in small letters, as in “xvi”, which is the traditional form for page numbers in a book’s front matter.
A line that is neither a plain whole number nor a valid numeral is reported as not valid. The check is strict: “IC” for 99 and “VX” for 5 are rejected, because proper numerals follow the subtraction rules.
A few handy ones
2026 is MMXXVI, 2000 is MM, 1999 is MCMXCIX, 49 is XLIX (not IL), and 14 is XIV. Super Bowl numbering uses them, and so does the year printed at the end of most film credits.
If you need the words for a number, the number to words converter writes it out. To find all the numbers in a text, use the number extractor, and for Roman numerals in uppercase or lowercase style, the case converter changes the case.