Screw Information and Screw sizing chart - hingedummy
As the number increases, so does the size of the entire screw, both head size and shaft size--but not length. Therefore, a #8 screw is about twice the size of a #4 screw, but may be the same length. Wake Up!-- This is important. Most wood screws have a common "pitch" to the threads, but some have a thread with a steeper incline.