Roman Numeral Converter online

How to Use the Roman Numeral Converter

1. Type an integer between 1 and 3,999, or a Roman numeral string.
2. Press Convert (or just keep typing — it converts live).
3. The big result shows the conversion; the smaller line tells you the direction.
4. Click Clear to reset the field.

Roman numerals are a sign-value system: each letter has a fixed value (I=1, V=5, X=10, L=50, C=100, D=500, M=1000) and the convention is that a smaller value placed before a larger one is subtracted. The greedy algorithm used here always produces the canonical short form — MCMXCIV for 1994, never the longer MDCCCCLXXXXIIII you sometimes see on building cornerstones.

How the Roman Numeral Converter Works

The detection is automatic: if your input parses as an integer it converts to Roman, otherwise it treats the input as Roman characters (case-insensitive) and converts to Arabic. Inputs outside 1–3,999 are flagged rather than silently truncated.

• Bidirectional auto-detection — no need to pick a mode
• Always emits the canonical subtractive form
• Case-insensitive on Roman input
• Out-of-range inputs are flagged, not silently truncated

Explore the full suite of Number tools and 290+ other free utilities at Chunky Munster.