What are Roman numerals?
Roman numerals are a numeral system originating in ancient Rome that uses letters to represent values: I=1, V=5, X=10, L=50, C=100, D=500, M=1000. Combinations of these form other numbers following a subtractive principle — IV=4 (one before five), IX=9, XL=40, XC=90. The system covers 1 to 3999 (MMMCMXCIX); numbers 4000 and above require extended notation. Roman numerals remain in use today for clock faces, book chapters, film sequel numbering, Super Bowl editions, and copyright year notices.
How to use this tool
- 1 In Number → Roman mode, type any integer from 1 to 3999 — the Roman numeral and its lowercase equivalent appear instantly.
- 2 Switch to Roman → Number mode and type a Roman numeral — the Arabic value and ordinal form are shown.
- 3 Roman input is case-insensitive: xiv and XIV are treated identically.
- 4 Click the copy button next to any output to grab it.
Frequently asked questions
Why does the system only go up to 3999?
Standard Roman numerals max out at MMMCMXCIX (3999) because there is no standard single character for 5000. Numbers from 4000 upward historically used a bar (vinculum) over a letter to multiply it by 1000, but that notation is not universally supported in Unicode.
What is the subtractive principle?
When a smaller value precedes a larger one, it is subtracted: IV = 5 − 1 = 4. Only six subtractive combinations are standard: IV (4), IX (9), XL (40), XC (90), CD (400), CM (900).
What is an ordinal number?
An ordinal number expresses position in a sequence: 1st, 2nd, 3rd, 4th. This tool shows the ordinal of the Arabic result so you can see both "2024" and "2024th" — useful when generating chapter headings or date suffixes.
What do lowercase Roman numerals look like?
Lowercase Roman numerals use the same letters in lowercase: i, v, x, l, c, d, m. They are used in document front matter (page i, ii, iii), footnotes, and some outline formats.
Is my data sent anywhere?
No. Conversion uses a fixed lookup table and arithmetic in your browser. Nothing is transmitted.