Number Base (Binary/Hex/Decimal) & Roman Numeral Converter

Convert Roman Numerals, Decimal, Binary, Hex, and Any Base 2–36

Roman numerals refuse to die. They still crown movie sequels, mark Super Bowls, date cornerstones, and number the chapters of books — and every few months someone needs to know what MCMXCIV actually means (1994, if your brain blanked). The system is beautifully logical once you see it: I, V, X, L, C, D, M stand for 1, 5, 10, 50, 100, 500, 1000, and you add values left to right — except when a smaller value sits before a larger one, in which case you subtract. That one twist gives us IV for 4, IX for 9, XL for 40, XC for 90, CD for 400, and CM for 900.

The same converter also speaks the number languages of computing. Binary (base 2) is how machines think, octal (base 8) shows up in Unix file permissions like chmod 755, decimal (base 10) is everyday arithmetic, and hexadecimal (base 16) paints every color on the web — #FF5733 is just three base-16 bytes for red, green, and blue. Supporting every base from 2 to 36 with digits 0–9 then A–Z covers every practical case, from converting a subnet mask to decoding a short URL slug. Once you see the same value in three bases side by side, the whole positional system clicks into place.

A few delightful quirks are worth knowing. Standard Roman numerals top out at 3999 (MMMCMXCIX) because there is no symbol for 5000 in common use. Clockmakers traditionally carve IIII instead of IV on clock faces — a centuries-old convention, possibly for visual symmetry with VIII on the opposite side. And the subtractive rule has limits: you write 8 as VIII, never IIX, and 90 as XC, never LXL. The converter enforces these rules both ways, so whether you are decoding a monument or encoding a chapter heading, the result follows classical convention.