Roman Numeral Converter
Convert numbers to Roman numerals and back (1–3999) — instantly, in your browser, with malformed-numeral validation.
Breakdown: MM + XX + IV = 2000 + 20 + 4
🔒 Converted in your browser. Roman numerals cover 1 to 3999.
Numbers ↔ Roman numerals
Type a number to see its Roman numeral, or type a Roman numeral to get the number — both update live. Roman
numerals represent 1 to 3999, and the tool validates input so malformed numerals like IIII or
VV are rejected rather than silently mis-parsed.
How Roman numerals work
Roman numerals combine the symbols I(1), V(5), X(10), L(50), C(100), D(500) and M(1000). Subtractive pairs like
IV (4) and IX (9) avoid four repeated symbols.
Frequently asked questions
Why only 1 to 3999?
Standard Roman numerals have no symbol above M (1000), so 3999 (MMMCMXCIX) is the largest value written with the classic letters.
Is there a zero in Roman numerals?
No. The Roman system has no symbol for zero, which is why the range starts at 1.
Does it catch invalid numerals?
Yes. It converts your input back and compares, so non-standard forms (IIII, IL, VV) are flagged as invalid.