Numbers to Roman numerals, and back
One field handles both directions — type digits to get the Roman numeral, or type a Roman numeral to get the number back. Covers the standard range of 1 to 3,999, and rejects non-standard forms like IIII rather than guessing what you meant.
How to use
- Type a number (1–3,999) or a Roman numeral into the field
- Press Convert
- Read the result, with the full symbol-by-symbol working shown below
Common questions
Do I need to select a direction, or does it detect what I typed?
It detects automatically — type digits and it converts to Roman numerals, type letters (I, V, X, L, C, D, M) and it converts back to a number. The two alphabets never overlap, so there's nothing to choose.
What's the largest number this supports?
3,999. Beyond that, Roman numerals traditionally used a bar over a symbol to multiply it by a thousand, a notation this tool doesn't attempt to reproduce.
Why did it reject a Roman numeral I typed, like IIII for 4?
It only accepts the standard subtractive form (IV, not IIII) — if what you typed doesn't round-trip back to itself through the standard conversion, it's rejected and the tool shows you the standard way to write that number instead.