Number Base Converter
Convert a number between binary, octal, decimal, hex, and any base 2–36.
About Number Base Converter
Number Base Converter shows a single integer simultaneously in binary (base 2), octal (base 8), decimal (base 10), hexadecimal (base 16), and any custom radix from 2 to 36. Type a value, tell it which base that value is written in, and every other base updates below — the right setup for the everyday work of cross-checking a hex constant against its bit pattern, pasting a decimal value into a tool that expects binary, or sanity-checking a permission mask.
Worked example: type 255 with the input base set to Decimal and the converter shows 11111111 (binary), 377 (octal), 255 (decimal), and ff (hex). The 0x, 0b, and 0o prefixes are accepted and stripped, but they are not auto-detected — set the input base to Hexadecimal and '0xff' reads as 255, while leaving it on Decimal reports the value as invalid. For bases above 16, letters A–Z stand for digits 10–35 — the same scheme JavaScript's parseInt and Java's Integer.parseInt use. Base 36, with the alphabet 0–9 + a–z, is the most compact representation that still uses only ASCII letters and digits.
Conversion is done with arbitrary-precision integers (BigInt), so there is no 64-bit overflow and no floating-point rounding — a 200-digit number converts exactly. Negative integers are supported (a leading minus sign round-trips correctly), and the input is case-insensitive (A and a both mean 10). For two's-complement bit-fiddling at a specific width (8-, 16-, 32-, 64-bit) you want a different tool.
Everything runs locally in your browser. Nothing about the value you convert is logged or uploaded.