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Roman Numerals Converter🔒 100% local
Numbers to Roman numerals. Privacy-first, no server uploads, no tracking.
Converts an integer between 1 and 3999 into Roman numerals and then reads its own result back as a number to confirm the round trip. The conversion uses the standard subtractive pairs (IV, IX, XL, XC, CD, CM). The number you type is processed in the page and is not sent to a server.
How to use it
- Type a whole number such as 2024 into the input box.
- Press Process. The output shows the number, the Roman form, and a reverse check line with a tick or a mismatch marker.
- Copy the result or press Clear to start again.
Worked example
2024becomesInput: 2024
-> Roman: MMXXIV
Reverse check: "MMXXIV" -> 2024 (match)Computed in Node. The page prints an arrow glyph and a tick mark; they are shown here as -> and (match).
3888becomesInput: 3888
-> Roman: MMMDCCCLXXXVIII
Reverse check: "MMMDCCCLXXXVIII" -> 3888 (match)When to use it
- Writing a year, chapter number or copyright line in the traditional numeral form.
- Working out the numeral for a milestone number for a poster or a tattoo before it is committed to ink.
- Converting the other way in your head is error-prone, so checking a numeral you already have against its value.
What it does not do
- It is one-directional in practice. You supply an Arabic number and get the numeral; there is no mode that accepts 'XIV' and returns 14, even though the reverse-check code could read one.
- The range is 1 to 3999. Zero, negatives and 4000 and above are rejected with 'Enter an integer 1-3999', so there is no vinculum or overline notation for larger values.
- Input is parsed with parseInt, so '12abc' is read as 12 and '3.9' is read as 3 rather than being flagged as invalid.
- The check it prints is its own parser reading its own output, which cannot catch a shared misconception - it confirms internal consistency, not correctness against an outside source.