Stud Calculator
Studs = ⌈wall length × 12 ÷ spacing⌉ + 1. A 10 ft wall at 16 in on center: ⌈7.5⌉ + 1 = 9 studs, 10 studs with 10 % waste, 30 ft of plates. A 12 ft wall takes 10 studs at 16 in and 7 at 24 in; add one per corner and two per door or window.
Studs to buy
10 studs
9 before 10 % waste
Estimate only. Check dimensions, loads and local code requirements with a qualified professional before you build.
- Studs along the walls
- 9
- Plates (3 rows)
- 30 linear ft
- Stud lumber
- 10 studs × 8 ft = 80 linear ft
Estimate only, verify with a professional: the tool counts studs, it does not check what a wall can carry. Headers, cripples and blocking are not counted.
Checked by the Yardstick Math team · How we check
Worked examples
10 ft wall at 16 in on center
- 10 × 12 ÷ 16 = 7.5, rounded up to 8
- 8 + 1 end stud = 9 studs
- 9 × 1.10 = 9.9, rounded up to 10 with waste
- Plates = 10 × 3 = 30 ft
Result: 9 studs (10 with 10 % waste) and 30 ft of plates.
Checked by the automated test “stud — 10 ft wall at 16 in → ⌈7.5⌉ + 1 = 9 studs, plates 30 ft; 12 ft → 10, at 24 in → 7”.
Rounding wall by wall
- At 16 in: 12 ÷ 16 = 0.75 stud per foot + 1 at the end
- Two 10 ft walls: 9 + 9 = 18 studs
- One 20 ft wall: ⌈15⌉ + 1 = 16 studs
Result: Two walls take 18 studs, one wall of the same total length 16.
Checked by the automated test “stud — per foot at 16 in: 12 / 16 = 0.75 stud per foot + 1 at the end; rounding wall by wall (two 10 ft walls = 18, one 20 ft wall = 16)”.
How it works
Studs per wall = ⌈length × 12 ÷ spacing⌉ + 1
Studs = Σ walls + corners + 2 × openings
To buy = ⌈studs × (1 + waste ÷ 100)⌉
Plates (ft) = wall length × plates (1 bottom + 2 top = 3)
Assumptions
- Corners and openings follow the standard wall described by Building Science Corp.: “a 2x4 frame at 16 inch centers with double top plates, three stud corners, jack studs”.
- One extra stud per corner (three-stud corner) and two per opening (king + jack); headers, cripples and blocking are not counted.
- Spacing depends on what the wall carries: in IRC Table R602.3(5), a 2 × 4 bearing wall goes to 24 in under a roof only and 16 in under one floor.
- The tool counts studs; it does not check a wall's strength.
Reference table
| Wall length | 16 in on center | 24 in on center |
|---|---|---|
| 8 ft | 7 | 5 |
| 10 ft | 9 | 6 |
| 12 ft | 10 | 7 |
| 16 ft | 13 | 9 |
| 20 ft | 16 | 11 |
| 40 ft | 31 | 21 |
One stud at each end of the wall.
Before you buy
- One line per wall. Studs are rounded wall by wall, as on the plan.
- Stud length. Wall height minus the plates.
- Load. What spacing a wall may use depends on what it carries: ask your building department or a professional.
Common mistakes
- Forgetting the end stud A 10 ft wall at 16 in has 7.5 spaces: 8 studs start them and one more closes the wall, 9 in all.
- Using 0.75 per foot for the whole house Round each wall on its own: two 10 ft walls take 18 studs, not the 16 of one 20 ft wall.
- 24 in under a floor IRC Table R602.3(5) allows a 2 × 4 bearing wall at 24 in under a roof only, 16 in when it also carries one floor.
- Leaving out corners and openings Each corner adds a stud and each door or window two (king and jack) in the standard wall BSC describes.
Frequently asked questions
How far apart are studs?
Usually 16 in on center, sometimes 24 in: DOE notes that 2 × 4 studs in walls supporting only a roof and ceiling can be spaced up to 24 inches on-center, except Utility grade (No. 3) studs. Under one floor, IRC Table R602.3(5) keeps them at 16 in.
How many studs in a 10 foot wall?
9 at 16 in on center (⌈120 ÷ 16⌉ + 1) and 6 at 24 in, before corners, openings and waste.
How many studs for a 12 foot wall?
10 at 16 in on center and 7 at 24 in, one at each end included.
How many studs per foot?
0.75 per foot at 16 in (12 ÷ 16), plus one at the end of each wall; 0.5 per foot at 24 in.
How many studs do I need?
Round each wall up to whole spaces and add one, then one per corner and two per door or window, plus about 10 % waste: a 10 ft wall at 16 in comes to 10.
Sources
Formula, examples and sources checked on by the Yardstick Math team. How we check our formulas.
- IRC 2021 Table R602.3(5): Size, height and spacing of wood studs — International Code Council, via UpCodes, accessed
- Advanced Wall Framing — U.S. Department of Energy, accessed
- BSI-030: Advanced Framing — Building Science Corporation, accessed