Roman Numeral Converter
Convert numbers to Roman numerals and back, from 1 to 3999, with a breakdown of how each numeral is built.
About this calculator
This converter works in both directions — type a number from 1 to 3999 to get its Roman numeral, or type a numeral to get the number back. The breakdown underneath shows how the result is assembled from its parts, which is usually more useful than the answer on its own if you are trying to learn the system or check a piece of homework.
Roman numerals still turn up in plenty of everyday places: chapter and volume numbers, clock faces, film and game sequels, the copyright date at the end of a broadcast, monument and building inscriptions, Super Bowl numbering, and outline numbering in formal documents. They are also a staple of primary and middle-school maths.
Conversion from a numeral is validated strictly rather than loosely. A string like IIII or IC can be read as 4 and 99 if you are being generous, but neither is valid notation, and quietly accepting them would make this useless for checking whether an answer is actually right. When the input is not canonical, the tool says so and shows the correct form.
Frequently asked questions
Seven letters carry fixed values: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1000. Values are added when written largest to smallest, so XVI is 10 + 5 + 1 = 16. When a smaller letter comes before a larger one it is subtracted instead, which is how IV means 4 and CM means 900.
Standard notation never repeats a letter more than three times, so 4 uses the subtractive form IV rather than IIII. You will still see IIII on some clock faces — that is a traditional stylistic choice, not correct notation, and this converter flags it as invalid.
In plain text, 3999 (MMMCMXCIX). Larger values need a vinculum — an overline that multiplies a numeral by 1000 — which cannot be typed as ordinary characters, so most converters, including this one, stop at 3999.
No. The system was built for counting and has no symbol for nothing. Medieval scholars wrote the Latin word nulla when they needed to express zero in a Roman-numeral context.
Only six: IV (4), IX (9), XL (40), XC (90), CD (400) and CM (900). A subtraction is only valid one power of ten below the larger symbol, which is why IC is not a valid way to write 99 — that is XCIX.
Convert it like any other number: 2024 becomes MMXXIV, and 1987 becomes MCMLXXXVII. Type the year into the converter above and the breakdown shows exactly how each part is formed.
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