You'll have to shift the values around anyway, so: int intermediate = byte_or_word << N; // N chosen to put the five bits in the highest positions in the int.

You'll have to shift the values around anyway, so: int intermediate = byte_or_word << N; // N chosen to put the five bits in the highest positions in the int. int value = intermediate >> bits_per_int - 5; Instead of masking rely on arithmetic shift right to keep the sign bit.