How many studs do you need? Enter wall length and spacing to see studs to buy, with extras for corners, doors and windows, plus plates and stud length for your wall height.
How to use the stud calculator
- Enter the length of one wall. For a room, run each wall in turn, or add the lengths and count every corner once.
- Pick the stud spacing from your plans. 16 in on center is the usual layout.
- Pick the wall height. The three standard heights use precut studs; choose Other height to enter your own.
- Enter the corners, doors and windows, and change the extra studs for each to match the way you frame them.
- Keep some extra for crooked boards, choose the length of the plate boards and add prices if you want a total.
Stud formulas
Layout studs = wall length (in) ÷ spacing (in), rounded up, + 1 Studs = (layout studs + corners × extra per corner + openings × extra per opening) × (1 + extra %), rounded up Plates (linear ft) = wall length (ft) × 3 with a double top plate, or × 2 with a single Stud length = wall height − 1 1/2 in per plate
The + 1 is the stud at the far end of the wall. Plates are 2× lumber, which dresses to 1 1/2 in thick under the American Softwood Lumber Standard, so a single bottom plate and a double top plate take up 4 1/2 in of the wall height.
Worked example: a 20 ft wall with one window, 16 in on center
- Layout: 20 × 12 = 240 in, and 240 ÷ 16 = 15, plus 1 = 16 studs.
- Window: + 2 studs = 18 studs.
- 10% extra: 18 × 1.10 = 19.8, so buy 20 studs of 92 5/8 in for an 8 ft ceiling.
- Plates: 3 × 20 = 60 linear ft, or 66 ft with 10% extra: 5 boards of 16 ft.
Studs per wall length
Layout studs only, before corners, openings and extra:
| Wall length | 12 in on center | 16 in on center | 24 in on center |
|---|---|---|---|
| 8 ft | 9 | 7 | 5 |
| 10 ft | 11 | 9 | 6 |
| 12 ft | 13 | 10 | 7 |
| 16 ft | 17 | 13 | 9 |
| 20 ft | 21 | 16 | 11 |
| 24 ft | 25 | 19 | 13 |
| 30 ft | 31 | 24 | 16 |
| 40 ft | 41 | 31 | 21 |
Precut stud lengths
| Ceiling | Precut stud | Wall height with 3 plates |
|---|---|---|
| 8 ft | 92 5/8 in | 97 1/8 in (8 ft 1 1/8 in) |
| 9 ft | 104 5/8 in | 109 1/8 in (9 ft 1 1/8 in) |
| 10 ft | 116 5/8 in | 121 1/8 in (10 ft 1 1/8 in) |
Precut studs leave room for a single bottom plate and a double top plate, and a little for the ceiling drywall, according to the Math Encounters blog. With a single top plate the wall is 1 1/2 in lower.
How far apart can studs be?
Under IRC Table R602.3(5), as summarized by the City of Blaine, Minnesota, 2×4 bearing studs up to 10 ft tall may be 24 in on center when they carry only a roof and ceiling, but no more than 16 in when they also carry a floor. 2×4 non-bearing studs may be 24 in apart and up to 14 ft tall. Lower stud grades, your plans and local amendments can set tighter limits.
Tips for framing a wall
- Lap the double top plate. The Journal of Light Construction notes that most codes want the double top plates of bearing walls lapped so the splices are at least 4 ft apart, and lapped at corners and intersections.
- Count shared corners once. When you run the calculator wall by wall, add each corner to only one of the two walls.
- Treat the extra studs as an allowance. Corner styles and opening details vary. The layout studs that fall inside an opening are usually cut down into cripples, so they are not wasted.
- Headers are separate. Size headers from your plans or the header tables; the board foot calculator can price them.
Questions
How many studs do I need for a 10 ft wall?
9 studs at 16 in on center (120 ÷ 16 = 7.5, rounded up to 8, plus 1), or 6 at 24 in, before corners, openings and extra.
How many studs are in a 20 ft wall?
16 at 16 in on center and 11 at 24 in on center, before corners, openings and extra.
What length studs do I need for an 8 ft ceiling?
92 5/8 in precut studs. With a single bottom plate and a double top plate the wall comes to 97 1/8 in.
Should studs be 16 or 24 inches on center?
16 in is the common layout and the limit for 2×4 bearing walls that carry a floor as well as the roof and ceiling. 24 in is allowed in many walls that carry only a roof and ceiling, and in non-bearing walls; check your plans and local code.
How many studs for a 12 ft wall at 16 in on center?
12 × 12 ÷ 16 = 9 spaces, plus 1 end stud = 10 studs before extras for corners and openings.
Sources
- Basic Wood Framing, City of Blaine, Minnesota.
Used for: Stud size, height and spacing limits from IRC Table R602.3(5). - JLC Field Guide: Wall Framing, Journal of Light Construction, Jan 1, 2023.
Used for: Double top plates lapped with splices at least 4 ft apart. - Voluntary Product Standard PS 20-20: American Softwood Lumber Standard, NIST / American Lumber Standard Committee.
Used for: 2× lumber dresses to 1 1/2 in thick (a 2 × 4 is 1 1/2 × 3 1/2 in). - Stud Length Requirements, Math Encounters Blog, May 9, 2016.
Used for: Precut stud lengths of 92 5/8, 104 5/8 and 116 5/8 in for 8, 9 and 10 ft ceilings.