Clock faces, movie credits, book chapters and the Super Bowl all still use Roman numerals. This converter turns a number into its Roman numeral and reads a Roman numeral back as a number, and it does both at the same time as you type. It follows the standard written form that is used today, so the results match what you would see on a monument or a title page.
Convert in three steps
- Type a whole number from 1 to 3999 into the Number box, or a numeral into the Roman numeral box.
- The other box fills in at once. If the numeral is invalid, a message tells you what is wrong.
- Press Copy to take the numeral with you.
The seven symbols
- I is 1, V is 5 and X is 10.
- L is 50, C is 100 and D is 500.
- M is 1000.
How the rules work
Symbols are added from the largest to the smallest, so VIII is 5 + 3 = 8. A smaller symbol placed before a larger one is subtracted, which is why IV is 4, IX is 9, XL is 40, XC is 90, CD is 400 and CM is 900. Only I, X and C can be subtracted, and only from the next two larger symbols. A symbol is never repeated more than three times in a row, so 4 is IV and not IIII, and 1994 is MCMXCIV.
You will meet Roman numerals on building cornerstones that give a year, in the names of kings and popes such as Elizabeth II, in outlines with sections I, II and III, and on sports events. Reading a year like MMXXIV quickly takes practice, which is where a converter saves time.
Why only up to 3999
The seven symbols reach 3999, written MMMCMXCIX. Larger numbers were written in the Middle Ages with a bar over a symbol to multiply it by 1000, but that notation is rare and not standard, so the tool stays with the classic range. There is also no symbol for zero. Nothing you type leaves your browser.