Wall studs are spaced using 16 or 24 inches between each other, measured at the center of the stud. The spacing serves a variety of functions, including supporting ceiling beams adequately and providing the space needed to install insulation.
The spacing of the studs is designed so that the other materials being used and the studs can easily be matched. Plywood for the exterior and drywall for the interior walls comes in 4-foot sheets, so they can easily be uniformly attached using the 16-inch centers without having to trim the pieces.
When using 2-by-6 pieces of lumber for framing, some builders use 26 inches between the centers of the studs. The 2-by-6 pieces are sturdier, and most local codes allow for the difference in strength as opposed to that of 2-by-4 pieces.
Advantages of using a 24 inch spacing include less lumber usage, a bigger insulating space and a design that matches up with the spacing of roof rafters, giving load bearing support down to the foundation, as noted by the Chicago Tribune.
When trying to locate studs, the spacing helps as all that is necessary to find the location of any stud in a wall is the location of one of them and then measuring to either side.