Convert numbers between binary, octal, decimal and hexadecimal all at once. Whether you are reading a hex color, decoding a permission mask, working with bit flags or just checking an assembly listing, being able to see the same value in every common base saves constant mental arithmetic. Type a value into any of the four fields and the other three update instantly, so you never have to run a separate conversion. It validates that your input contains only digits legal for that base, so mistakes are caught immediately rather than producing a wrong answer. Enter a number in whichever base you have. All conversion runs locally in your browser, with nothing sent to a server.