How the stud count works
Studs are laid out at a fixed spacing from one end of the wall, measured to the center of each stud. Divide the wall length by the spacing, round up, and add one for the stud at the far end. Then add studs for corners and openings, and a few extra for crooked or split boards.
layout studs = ⌈wall length ÷ spacing⌉ + 1
studs = (layout studs + 2 × corners + 2 × openings) × (1 + waste %)
Worked example
A 20 ft wall at 16 in on center: 240 ÷ 16 = 15, plus one, gives 16 layout studs. Two corners and one window add 6, making 22. With 10 percent for culls you buy 25 studs. The plates (one bottom and a doubled top) need 60 linear feet. At 24 in on center the same wall needs 11 layout studs and 19 to buy. A 6 m wall at 600 mm centers also needs 11 layout studs and 19 to buy, with 18 m of plate.
Standard stud spacing
| Spacing | Where it is used |
|---|---|
| 16 in (406 mm) on center | The usual US and Canadian default for walls |
| 24 in (610 mm) on center | Many 2×6 exterior walls and non-bearing walls, where code allows |
| 400 mm and 600 mm | Metric layouts that fit 1200 mm sheets |
| 450 mm | Common in Australian wall framing |
Both 16 and 24 in divide evenly into 48 in, so the edges of 4 × 8 sheets of drywall and sheathing land on a stud. The allowed spacing depends on stud size, wall height and the load the wall carries, so check local code before you change it.
Why corners and openings need extra studs
- Corners and junctions. Where two walls meet, you need extra framing so both walls and the drywall inside the corner have something to fasten to. Two extra studs per corner is a common allowance.
- Openings. Each window or door gets a king stud on each side running full height, plus jack (trimmer) studs under the header. Some layout studs fall inside the opening and are left out, so two extra per opening is a fair average. Wide openings or doubled jacks need more.
- Cripples and blocking above headers and below sills are short pieces, often cut from offcuts. Add a few studs if you have many openings.
Precut stud lengths
| Wall | Precut stud | Wall height with 3 plates |
|---|---|---|
| 8 ft ceiling | 92 5/8 in | 97 1/8 in |
| 9 ft ceiling | 104 5/8 in | 109 1/8 in |
Precut studs assume one bottom plate and two top plates, each 1½ in thick. The extra height above 8 or 9 ft leaves room for the ceiling drywall and floor finishes.
Metric layouts
In metric, choose 400 mm or 600 mm centers so the edges of 1200 mm sheets fall on studs, or 450 mm where local practice and the lining allow it. Enter the wall length in meters and the calculator does the same count.
Plates and sill plates
Plates are bought by length. The 60 linear feet in the example is four 16 ft boards. Splice top plates over a stud and offset the joints in the doubled top plate so they do not line up. Where a bottom plate sits on concrete, the IRC requires pressure-treated or naturally durable lumber in most cases, often with a sill sealer underneath. Check local code.
Tips
- Mark the layout on the plates before you nail anything. Most tape measures highlight 16 in spacing so this goes quickly.
- Sight down each stud and set aside badly bowed or twisted ones for blocking.
- Load-bearing walls, headers and shear walls are structural. Follow your local code and get a permit where required.
Frequently asked questions
How many studs do I need for a 20 ft wall?
At 16 in on center a 20 ft wall has 16 layout studs. With two corners, one opening and 10 percent extra, buy 25. At 24 in on center, buy 19.
What is the formula for studs?
Divide the wall length in inches by the spacing, round up and add one. Then add about 2 per corner and 2 per opening, and 10 percent for waste.
How much plate do I need?
Three times the wall length for one bottom plate and a doubled top plate. A 20 ft wall needs 60 linear feet.