With n bits, exactly 2ⁿ different states can be represented—unsigned, that is, from 0 to 2ⁿ−1.

Bit 1 Bit → 0…1
Nibble 4 Bit → 0…15
Byte 8 Bit → 0…255
Halfword 16 Bit → 0…65535
Word 32 Bit → 0…4 294 967 295

Mnemonic: n bits → 2ⁿ combinations, maximum value 2ⁿ−1