How to Use This Tool
Enter the wall, then say how many corners, T-intersections and openings it has. Those three things are the whole difference between the formula and the delivery.
What the formula misses
Length over spacing plus one gives the field studs — the evenly spaced ones in an uninterrupted run. Everything else is forced by geometry:
A corner needs backing so that drywall has something to fasten to on both walls, which is two extra studs in the common three-stud detail. A T-intersection needs the same for the wall meeting it. Every opening needs two king studs running full height and two jack studs carrying the header, and then cripples above the header at the same spacing as the field, plus cripples below a window sill.
12 ft wall, 16 in centres, one 3 ft door, one corner
field studs 144 / 16 + 1 = 10
removed in opening 36 / 16 = -2
king + jack 2 + 2 = +4
cripples above 36 / 16 -> 3 = +3
corner = +2
----
total = 17
the formula alone = 10
difference = +70%
Wider spacing saves less than it looks
Going from 16 to 24 inch centres removes field studs but changes none of the corners, kings, jacks or cripples. On a short wall with an opening that can be a saving of only two or three studs, and it comes with consequences: 24 inch spacing needs thicker drywall on ceilings to avoid sag, gives less nailing surface for trim, and is not permitted for some load conditions.
Plates are three times the wall length
Standard platform framing uses a single bottom plate and a doubled top plate, so a 12 ft wall needs 36 linear feet of plate stock. The upper top plate laps over intersecting walls to tie them together, which means it cannot simply be cut to the wall length — allow for the laps.
Headers are a separate decision
Header size depends on the opening width, whether the wall is load bearing, and what is above it. A 3 ft opening in a non-bearing partition needs almost nothing; the same opening in a bearing wall under a roof needs a sized beam. That is a span-table and code question, not an arithmetic one, and it is the part of framing worth getting checked.
Buy a few more than the count
Framing lumber is not uniform. Every bundle contains a few pieces with a crown, a twist or a split end that belong in blocking rather than in a wall, and cutting cripples from a bowed stud just moves the problem. Ten per cent over is the usual allowance.
