How to use the stud calculator
- Add one row for each wall with its length and height. If the wall has doors or windows, enter how many and their typical width.
- Pick the stud spacing: 12, 16, 19.2 or 24 inches on center. Enter the number of corners and T-intersections in the project.
- Choose whether the wall has a double top plate and the length of plate boards you will buy. Keep the 5% waste or change it.
- Read the studs to buy, the stud cut length, the plate boards and the header lumber. Copy the shopping list for the lumber yard.
Formula
Studs in a wall run = ceil(wall length / spacing) + 1
Net studs for one opening = 4 - floor(opening width / spacing)
Extra studs = corners x studs per corner + T-intersections x studs per T
Studs to buy = (all walls + extras) x (1 + waste percent / 100), rounded up
Stud cut length = wall height - number of plates x plate thickness
Header length = (opening width + 3 in) x number of plies
Plate boards = every wall run, once per layer, packed into stock lengths
The first stud sits at one end of the wall, the others follow every spacing, and an extra stud closes the far end. Each opening adds two king studs and two jack studs and removes the grid studs that would have stood inside it. The 3 inches in the header formula is the thickness of the two jack studs the header rests on.
Worked example: four walls of a 12 by 10 foot room at 16 inches
A 12 ft wall is 144 inches, which is 144 / 16 = 9 bays, so 10 studs. A 10 ft wall is 7.5 bays, rounded up to 8, plus one gives 9 studs.
A 3 ft opening adds 4 studs and removes floor(36 / 16) = 2 grid studs, a net of 2. The two walls with an opening have 12 and 11 studs, and the plain walls have 10 and 9, for a total of 42.
Four corners at 2 extra studs each add 8, giving 50 studs. With 5% waste that is 52.5, so you buy 53 studs. With 3 plates (one bottom, two top) each 8 ft wall cut to 96 - 4.5 = 91.5 inches.
The plates run 44 ft per layer, or 132 ft over three layers. Packed into 12 ft boards, none of the 10 ft runs can share a board with another run, so you need 12 boards, and 13 with waste. The two 3 ft openings need (36 + 3) / 12 x 2 plies x 2 = 13 linear feet of header.
On center spacing
On center means the distance from the center of one stud to the center of the next. Sixteen inches is the most common spacing for load-bearing walls because it matches the width of sheet goods, and 24 inches is used where the design allows it. A smaller spacing needs more studs, so it costs more but stiffens the wall. Your plans or your local code decide which spacing applies.
Because 4 foot sheets of drywall and sheathing break on a stud center, many builders also keep the first stud in line with the end of the wall. The count above does this by placing a stud at the start and one at the end.
Corners, openings and plates
Corners need extra studs to nail the walls together and give a surface for the drywall. How many extra depends on the corner style, so this tool lets you set the number per corner. Openings need king and jack studs at each side and a header across the top. The tool counts them and the header lumber, but it does not size the header, which depends on the span and the load above it.
Plates run along the top and bottom of every wall. Most walls have one bottom plate and two top plates, which tie the walls together at the corners. The tool packs the plate runs into the board length you choose, so short walls share boards where they can.
What is not counted
Cripple studs above and below windows, sill plates, fire blocking, drywall backing and bracing are not in the count, and neither are the extra studs at wall ends that meet a chimney or beam. A framing plan or a quick walk-through with your lumber supplier will catch those.
Assumptions and limits
- Studs are at one fixed spacing along each wall. Different spacings in one wall need two rows.
- Opening studs follow a simple rule: four added, minus the grid studs it covers. Real framing plans can differ.
- The 2 extra studs per corner and 2 per T-intersection are example values you can edit.
- Plates are straight boards. Splices within a wall are only added when a wall is longer than a board.
- This is a quantity estimate. Lumber size, grade, headers and bracing come from your plans and local code.
Frequently asked questions
How many studs do I need for a wall?
Divide the wall length in inches by the spacing, round up, and add one. A 12 foot wall at 16 inches on center takes 10 studs before openings and corners.
What is 16 inches on center?
It is the distance from the center of one stud to the center of the next. Studs are 1.5 inches thick, so the gap between neighbors is 14.5 inches.
How many studs does a window or door add?
A framed opening adds two king studs and two jack studs and removes the grid studs that would have stood inside it. For a 3 foot opening at 16 inches that is a net of two extra studs.
How long should a wall stud be for an 8 foot ceiling?
Subtract the thickness of the plates from the wall height. With one bottom plate and two top plates of 1.5 inches each, an 8 foot wall takes studs cut to 91.5 inches.
How do I calculate a header length?
Take the width of the rough opening and add 3 inches for the two jack studs that hold the header up. Multiply by the number of plies in the header.