Estimate the number of studs and linear feet of plate lumber for a wall from its length and stud spacing.
studs = (floor(wall_in ÷ spacing) + 1) × (1 + waste)
Studs are spaced 16″ or 24″ on center. Count is the wall length divided by spacing, plus one, plus extra for corners and openings.
A standard wall has one bottom plate and a double top plate — three times the wall length in plate lumber.
A 24 ft wall is 288 inches. At 16-inch on-center spacing: 288 ÷ 16 = 18, plus 1 for the end stud = 19 studs for the field. Then add extra for each corner (typically 2-3 studs per corner), each opening (king and jack studs plus cripples), and any partition intersections. The 15% waste factor roughly covers these extras on a simple wall.
For plates, a standard wall has a single bottom plate and a double top plate — three runs of 24 ft, or 72 linear feet of plate stock.
16″ on center is the common residential spacing. The 15% waste covers corners, openings, and blocking.
About 13 at 16″ on center, before extras for corners and openings.