How Many Studs Do I Need? (Wall Framing Formula + Chart)
Part of Decks, Fences & Roofing
Quick answer
Field studs = wall length in inches ÷ stud spacing (usually 16), rounded up, plus one for the closing stud at the end. A 10-foot wall at 16 inches on center needs 9 studs; a 20-foot wall needs 16. Add about 4 studs per door or window and 2 per corner, then 10% for waste. Plate lumber is the wall length × 3 (one bottom plate and a doubled top plate).
A framed wall is vertical studs sandwiched between horizontal plates — a bottom (sole) plate and a doubled top plate. To order lumber you need two numbers: how many studs, and how much plate. Both come straight from the wall's length and your stud spacing.
The stud formula
Studs = wall length (in inches) ÷ on-center spacing, rounded up, plus one. Work in inches, not feet: a 20-foot wall is 240 inches, and 240 ÷ 16 = 15, plus the end stud = 16 studs. (Dividing 20 ft by 1.33 ft rounds the wrong way and gives 17 — a common calculator error.) The "+1" is the closing stud at the far end of the run; "on center" (o.c.) means measured from the middle of one stud to the middle of the next.
How many studs by wall length
| Wall length | 12" o.c. | 16" o.c. | 24" o.c. | Plate lumber (3×) |
|---|---|---|---|---|
| 8 ft | 9 | 7 | 5 | 24 lin ft |
| 10 ft | 11 | 9 | 6 | 30 lin ft |
| 12 ft | 13 | 10 | 7 | 36 lin ft |
| 16 ft | 17 | 13 | 9 | 48 lin ft |
| 20 ft | 21 | 16 | 11 | 60 lin ft |
| 24 ft | 25 | 19 | 13 | 72 lin ft |
These are field studs only — the evenly spaced verticals plus the end stud. They don't yet include the extra studs around openings and corners.
Get your stud & plate countsWall Framing CalculatorCalculate how many studs and how much plate lumber a wall needs — from its length, height and stud spacing — including extra studs for doors, windows and corners, plus the total 2×4s to buy.OpenAdd studs for openings and corners
- Each door or window: add about 4 studs — two full-height king studs and two shorter jack (trimmer) studs that carry the header across the opening.
- Each corner or wall intersection: add about 2 studs for backing, so drywall has an edge to land on in the corner (a 3-stud corner, minus the line stud you already counted).
- Below window sills and above dropped headers you'll also cut cripple studs at the same spacing — small extras the calculator rolls into the waste allowance.
Plates: the horizontal lumber
Code (IRC R602.3.2) calls for one bottom plate and a doubled top plate on load-bearing walls, so plate lumber is about three times the wall length. A 20-foot wall needs 60 linear feet of plate — about four 16-foot boards. Some non-bearing partitions use a single top plate, which makes it twice the length.
Don't forget waste
Add about 10% to both the studs and the plate lumber for saw cuts, crowned or split boards, and layout tweaks — then buy a couple of extra studs beyond that. The wall framing calculator runs your exact length, height, spacing, openings and corners and returns the stud count, plate boards and the total pieces to buy.
FAQs
How many studs do I need for a 10-foot wall?
Nine studs at 16 inches on center: 120 inches ÷ 16 = 7.5, rounded up to 8, plus 1 for the end stud. At 24 inches on center it's 6 studs, and at 12 inches it's 11. Add 4 more for a door and 2 per corner.
How many studs are in a 12x12 room?
A 12×12 room is four 12-foot walls (48 linear feet). At 16 inches on center each wall takes 10 field studs, so about 40 studs, plus roughly 2 per corner (8) and extras for any door — call it 48–52 studs with waste. You'll also need about 144 linear feet of plate lumber.
How do I figure studs per linear foot?
At 16 inches on center it's about 0.75 studs per foot plus one end stud; at 24 inches on center about 0.5 per foot plus one. A rule of thumb framers use is roughly one stud per linear foot of wall once corners and a door are added in.
Is it 16 or 24 inches on center?
16 inches on center is standard for exterior and load-bearing walls and is required by code for most 2×4 bearing walls; it also lands 4-foot drywall and sheathing edges on a stud. 24 inches on center, usually with 2×6 studs, is allowed for many non-bearing partitions and advanced framing and uses about a quarter less lumber.