Roman Numeral Converter
Convert a number to Roman numerals, or decode Roman numerals back to a number, instantly. Free and private, right in your browser.
How Roman numerals work
Roman numerals build numbers from seven letters: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500, and M is 1000. You add letters from largest to smallest, except when a smaller value sits in front of a larger one, which means you subtract it (IV is 4, IX is 9, XL is 40). This Roman numeral converter goes both ways and validates as it goes, so it covers the standard range of 1 to 3999 and quietly rejects malformed input like IIII or VX.
Keep the answer you just worked out
You decode a date off a building or a movie credit, copy it somewhere, then need it again later. Relic is an encrypted, permanent memory for everything you copy, so that number, that name, and that one note stay searchable on every device, forever, end-to-end encrypted so only you can read them. The converter is free. Never re-deriving the same answer twice is the upgrade.
Frequently asked questions
How do I convert a number to Roman numerals?
Type a whole number into the "Number to Roman" field and the Roman form appears instantly, or paste numerals into the other field to decode them back to a number. Both sides work at the same time, so you can convert either direction without switching modes.
What is the largest number I can convert?
This tool covers the standard range of 1 to 3999, written with the seven letters I, V, X, L, C, D, and M. Anything outside that range is rejected, because the classic notation has no single symbol for values above 1000 without extra bar-over-letter conventions.
Do Roman numerals have a zero?
No. The system has no symbol for zero and no way to write negative numbers, which is one reason it was eventually replaced for arithmetic. That's also why the smallest value this converter accepts is 1.
Why does it reject something like IIII or VX?
Roman numerals follow strict rules: you add letters from largest to smallest, and a smaller letter before a larger one subtracts (IV is 4, IX is 9). This tool re-encodes whatever you type and checks it round-trips exactly, so malformed forms like IIII (should be IV) or VX get flagged as invalid.
What's a common use for decoding Roman numerals?
Reading the year off a building cornerstone, a book's copyright page, or a movie's closing credits, where dates are often set in numerals. Paste the letters in and you get the year back without counting on your fingers.