Roman Numeral Converter
/roman-numeralConvert between Roman numerals and Arabic numbers. Supports values up to 3999 with correct subtractive notation.
Roman numerals appear in outlines, movie credits, and watch faces, but converting them mentally is fiddly. This tool converts between Roman numerals and Arabic numbers up to 3999 with correct subtractive notation. Both directions are instant. Conversion happens locally on your device.
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FAQ
Frequently asked questions
Everything you need to know about roman numeral converter.
What is the largest number supported?
3999, written as MMMCMXCIX, which is the conventional limit of standard Roman numeral notation. Larger values were historically written with special overline notation that this tool does not use.
Are lowercase numerals accepted?
Yes. The Roman numeral input is case-insensitive, so i, v, x, and M are all accepted and normalized before conversion.
What is subtractive notation?
Small numerals placed before larger ones subtract, such as IV for 4 and IX for 9, instead of writing IIII. The tool always uses this standard compact form in its output.
Can I convert from Roman numerals to Arabic?
Yes. Paste a Roman numeral and the tool returns the Arabic number instantly, validating the input and rejecting malformed sequences such as VV or IIII.
Is the conversion done locally?
Yes. All conversion is simple arithmetic that runs entirely in your browser, so nothing you type is transmitted or stored anywhere.
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