Estimating a stud wall
Framing a wall takes more lumber than the simple stud count suggests: every window and door adds king and jack studs, every corner and intersecting wall needs backing, and the top and bottom need plates. This calculator turns the wall length, height, stud spacing and openings into a material list: studs, plate length and sheathing panels.
How the count works
- Layout studs = wall length ÷ spacing, rounded up, + 1
- Extra studs: 2 for each opening (king and jack studs off the regular layout) and 2 for each corner or intersection
- Studs to buy = layout + extras, plus a waste margin for crooked or split pieces
- Plates = wall length × number of plates (usually a bottom plate and a double top plate)
- Sheathing panels = wall area ÷ panel area, plus waste
Headers, cripple studs, blocking and fire blocking are not included; add them from your plans.
Worked example
A 20 ft exterior wall, 8 ft high, framed at 16 in on center, with two windows and a corner at each end.
- Layout: 240 ÷ 16 = 15, + 1 = 16 studs.
- Extras: 2 × 2 openings + 2 × 2 corners = 8.
- With 10% waste: 24 × 1.1 = 26.4, so 27 studs.
- Plates: 20 ft × 3 = 60 ft, for example four 16 ft boards.
- Sheathing: 160 sq ft ÷ 32 = 5 panels, plus waste = 6 sheets of 4 × 8 OSB or plywood.
Studs by wall length
At 16 in on center, 8 ft high, with two openings and two corners:
| Wall length | Studs | 4 × 8 panels |
|---|---|---|
| 8 ft | 17 | 3 |
| 12 ft | 20 | 4 |
| 16 ft | 24 | 5 |
| 20 ft | 27 | 6 |
| 30 ft | 36 | 9 |
| 40 ft | 43 | 12 |
16 or 24 inches on center
- 16 in on center is the default for load-bearing walls, gives a stiffer wall and matches 4 ft sheet goods.
- 24 in on center, part of “advanced framing”, saves about a third of the studs and leaves more room for insulation, which reduces thermal bridging. It requires stacking studs over joists and rafters, and thicker drywall may be needed to avoid waviness.
Buying tips
- Precut studs (92⅝ in for 2 × 4) give an 8 ft 1⅛ in wall with a single bottom and double top plate, which suits 8 ft drywall plus ceiling thickness.
- Sight down every board and set aside crowned or twisted pieces for blocking.
- Use pressure-treated lumber for bottom plates on concrete, as most codes require.