Roman Numeral Converter
Convert between numbers and Roman numerals in either direction.
How to use: Type a number to get Roman numerals, or type Roman numerals to get the number.
Symbols
How to use the Roman Numeral Converter
Roman numerals appear on clock faces, movie credits, building cornerstones, book chapters and the Super Bowl. They use seven letters, each with a fixed value, and the position of the letters decides whether values are added or subtracted.
Type a number between 1 and 3999 to see its Roman form, or type a Roman numeral to see the number. Both boxes update each other as you type, and errors are explained straight away. The standard form is enforced, so “IIII” and “VX” are rejected because they break the rules.
The rules are simple. Letters are written from largest to smallest and added together: XVI is 10 + 5 + 1 = 16. A smaller symbol placed before a larger one is subtracted, but only in six cases: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). A symbol may not be repeated more than three times in a row, which is why 4 is IV instead of IIII.
The system tops out at 3999 (MMMCMXCIX) because there is no standard symbol for 5000 in plain letters; larger numbers historically used a bar over the letter to multiply by a thousand. Roman numerals have no zero and no decimals. The reference table lists every symbol with its value so you can learn to read them yourself.
Frequently asked questions
Why is 4 written IV and not IIII?
The standard rule avoids repeating a symbol more than three times and uses subtraction instead. Some clock faces use IIII for visual balance.
What is the largest Roman numeral?
In standard notation it is MMMCMXCIX, which is 3999.
Is there a Roman numeral for zero?
No. The Romans did not have a symbol for zero.