Roman Numeral Converter

Convert Arabic numbers and Roman numerals both ways, with strict standard notation.

Enter a number or Roman numeral.

Every conversion happens in your browser. Nothing is uploaded to BroBroGo.

FAQ

What range does it support?

It supports the standard Roman numeral range from 1 to 3999: I through MMMCMXCIX. It does not use overlines or other extended notation.

Why are IIII or VX rejected?

The converter checks standard subtractive notation. Use IV for 4, IX for 9, XL for 40, XC for 90, CD for 400 and CM for 900.

Can I paste lowercase Roman numerals?

Yes. Lowercase letters are accepted and converted as uppercase. Spaces, punctuation and non-standard forms are rejected so the result stays unambiguous.

Decimal to Fraction ConverterTurn finite decimals and repeating decimals like 1.2(34) into the simplest exact fraction.Fraction to Decimal ConverterTurn fractions and mixed numbers like 1/8 or 2 1/4 into exact decimals.Binary/Hex ConverterConvert numbers between binary, hex, decimal, and octal — or turn text into bytes.Unit ConverterConvert length, weight, temperature, area, volume and speed between any units, instantly.