What range is supported?

Standard Roman numerals from 1 to 3999 (I to MMMCMXCIX). Numbers outside this range are not representable in standard Roman notation.

Does it validate Roman numerals?

Yes. The converter checks that the Roman numeral follows correct notation rules (e.g., no IIII) by round-tripping through decimal.

Convert between Roman numerals and decimal numbers. Includes a reference table.

How to use: Enter a number or Roman numeral to convert between the two formats.

Decimal (1-3999)

Roman Numeral

4IV

9IX

10X

40XL

50L

90XC

100C

400CD

500D

900CM

1000M