It also flags numerals written in a non-standard way, such as IIII or IC, and tells you the standard form. Dates, years and a printable chart are below the converter.
How Roman numerals work
Roman numerals use seven letters: I for 1, V for 5, X for 10, L for 50, C for 100, D for 500 and M for 1,000. A number is written from the largest value to the smallest, and the values are added: VIII is 5 + 1 + 1 + 1, or 8, and MDCLXVI is 1,000 + 500 + 100 + 50 + 10 + 5 + 1, or 1,666. No letter is repeated more than three times in a row in standard notation.
To avoid four repeats, a smaller numeral placed before a larger one is subtracted. Only six such pairs are used: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). So 1994 is M + CM + XC + IV, or MCMXCIV. Forms like IC for 99 or IM for 999 look logical but are not standard; Romanify reads them, then flags them and shows the accepted spelling.
Using the converter
Type in the box and the result appears as you type. Digits are converted to numerals and letters to a number, in either upper or lower case, and commas or spaces in large numbers are ignored. Under the result you can see each building block with its value, which is the quickest way to check a numeral for a tattoo, an engraving or homework. The date converter turns each part of a date into numerals separately and lets you pick the order and separator. The chart prints on its own, with the converter and site hidden.
Where you still see them
Roman numerals survive on clock faces, in the names of monarchs and popes, in book prefaces and chapter headings, outlines, film copyright years, building cornerstones, and the numbering of major sporting events. On clocks, four is often written IIII rather than IV, a tradition that balances the dial visually. The converter covers 1 to 3999, the range of standard notation; larger numbers historically used a bar over a numeral to multiply it by a thousand. Everything runs in your browser, and only your last entries are remembered on this device.
Frequently asked questions
What is the largest Roman numeral?
In standard notation, 3999 (MMMCMXCIX). Larger numbers used a bar over a letter to multiply it by 1,000, which is rarely needed today.
Is there a Roman numeral for zero?
No. The Romans had no numeral for zero; medieval writers sometimes used the word nulla or the letter N.
Why is 4 written IV and not IIII?
Standard notation uses subtraction: a smaller numeral before a larger one is subtracted. IIII still appears on many clock faces by tradition.
Is Romanify free?
Yes. The converter, dates and charts are free with no sign-up.
Does it work offline?
Yes. Everything is converted in your browser once the page has loaded.