Hex to Binary Converter

Hex to binary needs no arithmetic. Replace each hex digit with its four-bit pattern from this table and join them:

So A5 is 1010 and 0101, giving 10100101. Because every digit maps on its own, you can check any part of a long result against the table.

Datasheets, register maps and debuggers print values in hex, but the meaning sits in individual bits. Convert to binary to see which ones are set. A status byte of 3C is 00111100: counting from 0 at the right, bits 2, 3, 4 and 5 are on and the rest are off. A mask of F0 is 11110000, so it keeps the top four bits of a byte and clears the bottom four.

The converter returns the shortest binary form. It drops leading zeros and doesn't space the output into groups of four:

• 0F gives 1111, not 00001111
• 3C gives 111100, not 00111100
• 1F4 gives 111110100, not 0001 1111 0100

The full result should have four bits for every hex digit you typed. If it's shorter, add zeros on the left until it is. Skipping this step is the usual reason bit numbers end up off by a few places.

A 0x prefix is accepted (0x0F gives 1111) and spaces are removed. A # gives an error. Any other character ends the reading without a warning, so only the digits before it are converted.

The result is exact for values up to 1FFFFFFFFFFFFF. For a longer string, such as a hash, split it into chunks of up to 12 hex digits, convert each chunk, pad each result to four bits per digit, and join them. Since each hex digit maps to its own four bits, the joined string is the same as converting the whole value at once.