Convert Arabic numbers to Roman numerals and back, supporting 1–3999 with automatic validation.
Arabic → Roman
Roman → Arabic
FAQ
How large a range can Roman numerals represent?
This tool supports 1–3999. Classical Roman numerals have no standard form for zero or negative numbers; values above 3999 need an overline for thousands, which this tool does not use.
Why is my Roman numeral conversion wrong?
Roman numerals follow strict rules: the same symbol repeats at most three times, and subtractive pairs are limited (e.g. IV=4, IX=9). The tool validates and flags illegal forms.
Is my data uploaded?
No. Conversion is entirely local in your browser; nothing is sent anywhere.