Wall Stud Calculator
Stud count for a wall at 16 or 24 inch spacing, plus the plate lumber.
The count
Divide the wall length by the on-center spacing, round down, and add one for the far end. A 20-foot wall at 16 in OC is 240 / 16 + 1 = 16 studs. That's the bare minimum: every corner, door and window adds studs (kings, jacks, cripples), which is what the +10% buying figure roughly covers on a simple wall. Frame with many openings? Count those separately.
Plates
A standard framed wall has one bottom plate and a doubled top plate: three full lengths of plate lumber per wall. 16 in OC with 1/2 in sheathing is the default for load-bearing walls; 24 in OC is common for non-bearing interior partitions.