Roman ↔ Arabic numeral converter
Convert an Arabic number (from 1 to 3999) to Roman numerals, or Roman numerals to their Arabic value. Type in either field and the conversion appears instantly, with validation of the classic notation. Everything happens in your browser, and it includes a table with the value of each symbol.
How to convert Roman numerals
- Type a number from 1 to 3999 in the “Number” field to see it in Roman numerals.
- Or type Roman numerals in the other field to see their Arabic value.
- The conversion appears instantly in the other field as you type.
- Copy the result with the copy button.
- Check the reference table to see the value of each symbol.
Frequently asked questions
Which numbers can I convert?
Classic Roman numerals run from 1 to 3999 (from I to MMMCMXCIX). The Roman system has no symbol for zero or for negative numbers, and above 3999 you would need an overline (vinculum) that is not part of the standard notation in text.
How do Roman numerals work?
They are written with seven symbols: I (1), V (5), X (10), L (50), C (100), D (500) and M (1000). They are added from left to right, except when a smaller symbol comes before a larger one (subtractive notation): IV is 4, IX is 9, XL is 40, XC is 90, CD is 400 and CM is 900.
What is subtractive notation?
To avoid repeating a symbol four times, a smaller one placed before a larger one is subtracted: instead of IIII you write IV (5−1), and instead of VIIII you write IX (10−1). Only the combinations IV, IX, XL, XC, CD and CM are allowed.
Is it case-sensitive?
No. You can type Roman numerals in uppercase or lowercase (mmxxiv or MMXXIV) and they are interpreted the same. By convention they are shown in uppercase.
Does it check that the Roman numeral is correct?
Yes. It only accepts well-formed classic notation: it rejects invalid forms such as IIII, VV or IC. If what you type is not a valid Roman numeral, it lets you know.
How do you write the current year in Roman numerals?
2024 is MMXXIV and 2025 is MMXXV. Type any year in the “Number” field to see it instantly: it is handy for copyright dates, tattoos, clocks or titles.
Is anything sent to a server?
No. The conversion happens entirely in your browser with JavaScript and works offline once the page has loaded.