How many studs do you need?

How many studs do I need for a wall?

Divide the wall length in inches by the stud spacing, round up and add one for the end. A 20 ft wall at 16 inches on center is 240 ÷ 16 = 15 spaces, so 16 studs. Add two for each door or window (the jack and king studs around the opening) and about three for each corner or place where another wall meets it.

What length studs do I need?

For an 8 ft wall, buy precut studs of 92⅝ inches. With a bottom plate and a double top plate, each 1½ inches thick, the wall comes out at 97⅛ inches — just right for 8 ft drywall sheets and a ceiling. For 9 ft walls use 104⅝ inch studs, for 10 ft walls 116⅝.

How much lumber do I need for the plates?

Three times the length of the wall: one bottom plate and a doubled top plate. A 20 ft wall takes 60 feet of plate — four 16 ft boards. Use pressure-treated lumber for any bottom plate that sits on concrete.

16 or 24 inches on center?

Sixteen inches is the standard for most walls and gives drywall and siding more support. Twenty-four inch spacing ("advanced framing") uses fewer studs and leaves more room for insulation, but check that your code, drywall and siding allow it.

What about headers?

Every door and window in a load-bearing wall needs a header sized for its width and load — the IRC header tables or your engineer give the size. The calculator counts one header per opening; size them separately.

What is a stud length for a 12 ft wall?

Precut studs are made for 8, 9 and 10 ft walls. For a taller wall the calculator uses the wall height minus the 4½ inches of the three plates: 144 − 4.5 = 139.5 inches (11 ft 7½ in). Studs that long are not usually precut, so you buy 12 ft lumber and cut it, or order the length from your supplier.

How much does 24 inch spacing save?

On a 24 ft wall with three openings, studs 16 inches apart need 25 studs and studs 24 inches apart need 19, a saving of 6. The saving comes with conditions: the sheathing, drywall and the loads must be designed for it, and corners and openings still need their extra studs.

How the count is built

The studs in the field of the wall are the length in inches divided by the spacing, rounded up, plus one for the end. Each opening adds two studs in this estimate; a detailed takeoff counts a king stud and a shorter jack stud on each side of the opening. The plates are three times the wall length: a bottom plate and a doubled top plate. Corners and the places where one wall meets another need extra studs, usually about three each, to give a nailing surface; the calculator leaves those to you because they depend on the plan.

Worked example: a 24 ft wall with two windows and a door

Spacing of 16 inches on a 24 ft wall gives 19 field studs. Three openings add 6, so 25 studs in all, and 72 feet of plate: five 16 ft boards, or six 12 ft boards. At 24 inch spacing the field count drops to 13 and the total to 19. For an 8 ft wall the precut stud is 92⅝ inches, which with three plates of 1½ inches makes the wall 97⅛ inches high; the 9 and 10 ft wall studs are 104⅝ and 116⅝ inches.

Common mistakes

Forgetting the corner and intersection studs makes the order short. Buying 96-inch studs for an 8 ft wall is the classic mistake: the three plates add 4½ inches on top of the stud, so the wall comes out far taller than 8 ft; the precut 92⅝ inch stud gives a wall 97⅛ inches high. Another is leaving the headers out of the lumber list or using a header too small for the span and load; the calculator counts the openings but not the headers, which the code tables or an engineer size. Finally, the studs here assume 2×4 or 2×6 lumber at the same spacing, so the plate and stud counts do not change with the thickness of the wall.

Sources: precut stud lengths (92⅝, 104⅝ and 116⅝ inches) and the three-plate wall are standard North American practice; the 1½ inch actual thickness of a 2× board follows the American Softwood Lumber Standard (PS 20). Header sizes come from the IRC tables or an engineer. Related: lumber calculator, drywall calculator, rafter length calculator and insulation calculator.