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How the Stud Calculator works
The stud calculator tells you how many studs and how much plate stock one straight wall needs. Enter the wall length, the stud spacing (16" or 24" on center), any extra studs for corners, openings and wall intersections, and the length of the boards you will use for plates.
Studs on layout = wall length ÷ spacing, rounded up, plus one stud to close the far end. Add the extras to get the total. Plates are one bottom plate and a double top plate, so plate length = 3 × wall length; divide by the board length and round up to get the number of plate boards. A wall that divides exactly does not get an extra stud or board.
Example: a 20 ft (240") wall at 16" on center with one window. 240 ÷ 16 = 15, plus the end stud = 16 studs on layout. The window adds 2 king and 2 jack studs, so 4 extras make 20 studs. Plates: 3 × 20 ft = 60 ft, and 60 ÷ 12 = exactly 5 boards of 12 ft.
Layout studs that land in a door or window opening usually become cripples, so the count still covers them; headers, sills and blocking are not included. Plate boards assume offcuts get spliced into other runs, with top-plate joints offset at least 24" (IRC R602.3.2). Maximum stud spacing depends on stud size, wall height and what the wall carries (IRC Table R602.3(5)); check your local code, and buy a few spare studs for crooked or split ones.
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 for the end: a 20 ft wall at 16" on center has 16 studs on layout. Then add studs for corners, door and window openings and wall intersections. A quick rule of thumb is about one stud per foot of wall once those extras are counted.
Should studs be 16 or 24 inches on center?
16" on center is the most common and gives a stiffer wall for drywall, siding and cabinets. 24" uses fewer studs, but IRC Table R602.3(5) limits spacing by stud size, height and load: for example, 2x4 bearing walls that carry a floor above are limited to 16". Check the table and your local code before going to 24".
How many extra studs for corners and windows?
A corner usually takes 2 to 3 studs beyond the layout, depending on how it is framed. Each door or window needs at least one king stud and one jack stud on each side, so 4 extras; wide or heavy headers may need double jacks. Wall intersections take 1 to 2 more for backing. Enter the total under extra studs.
How many plates does a wall need?
Most walls get one bottom plate and a double top plate, so plate stock is three times the wall length. The double top plate ties walls together at corners and intersections, and IRC R602.3.2 requires its end joints to be offset at least 24". A 20 ft wall needs 60 ft of plate.