Quick answer: studs = wall length (in) ÷ spacing, rounded up, + 1. Then add 2 per corner, 4 per opening (2 king + 2 jack) and about 10% for waste. A 20 ft wall at 16 in O.C. starts with 16 studs.
Parts of a framed wall
- Bottom (sole) plate: the board on the floor that the studs stand on.
- Top plates: usually doubled; the second plate overlaps joints and ties walls together at corners.
- Common studs: the vertical members at regular spacing, 16 or 24 in on center.
- King and jack studs: at each side of an opening; the jack (trimmer) holds up the header.
- Header: the beam over a window or door that carries the load around the opening.
- Cripples and sill: short studs above the header and below the window sill.
How to calculate studs
- Common studs: wall length in inches ÷ spacing, rounded up, + 1 for the end.
- Openings: take out the common studs that fall inside each rough opening, then add 2 kings and 2 jacks per opening. Cripples are usually cut from offcuts and the removed studs.
- Corners and intersections: add about 2 studs each for backing (a three-stud corner or a ladder or California corner).
- Waste: add 10% for crooked studs, blocking and mistakes.
Studs = (⌈L × 12 ÷ OC⌉ + 1) − studs in openings + 4 × openings + 2 × corners
Stud count chart
Common studs for a straight wall with no openings or corners.
| Wall length | 16 in O.C. | 24 in O.C. |
|---|---|---|
| 8 ft | 7 | 5 |
| 10 ft | 9 | 6 |
| 12 ft | 10 | 7 |
| 16 ft | 13 | 9 |
| 20 ft | 16 | 11 |
| 24 ft | 19 | 13 |
| 30 ft | 24 | 16 |
| 40 ft | 31 | 21 |
A quick rule of thumb some framers use is “one stud per foot of wall” at 16 in O.C. once openings and corners are included. The calculator gives you the actual count.
Windows, doors and headers
Enter the rough opening width, which is the size of the framed hole, usually about ½–1 in larger than the window or the door unit. Door rough openings are typically the door width plus 2 in (a 36 in door gets a 38 in opening).
Each header is 3 in longer than the opening, because it sits on a 1½ in jack stud at each end. The calculator lists the header length as a doubled member (two pieces, plus a spacer in a 2×4 wall). Size the header from IRC Table R602.7 or your engineer’s plans.
| Opening | Typical rough opening | Header length (each ply) |
|---|---|---|
| 32 in door | 34 in | 37 in |
| 36 in door | 38 in | 41 in |
| 3 ft window | 36½ in | 39½ in |
| 6 ft patio door | ≈ 74 in | ≈ 77 in |
Plates and stud length
With one bottom plate and a double top plate, the plates add 4½ in to the wall height. So the studs are the wall height minus 4½ in:
| Framed wall height | Stud length (3 plates) | Common precut |
|---|---|---|
| 8 ft (97⅛ in framed) | 92⅝ in | 92⅝ in |
| 9 ft (109⅛ in framed) | 104⅝ in | 104⅝ in |
| 10 ft (121⅛ in framed) | 116⅝ in | 116⅝ in |
Plate linear feet are the wall length × the number of plates. Buy the longest straight boards you can (often 16 ft) and stagger the joints in the top plates by at least 24 in, or as your code requires.
Worked example
A 20 ft exterior wall, 8 ft high, 2×4 at 16 in on center, one 3 ft window, a corner at each end. These are the calculator’s starting values.
- Common studs: 240 ÷ 16 = 15, + 1 = 16.
- Window: removes 2 common studs and adds 2 kings + 2 jacks: 16 − 2 + 4 = 18.
- Corners: 2 × 2 = 4 more: 22 studs; with 10% waste, 25 studs of 92⅝ in.
- Plates: 20 ft × 3 = 60 lin ft = 6 boards of 16 ft (two per row).
- Header: (3 + 0.25) × 2 = 6.5 lin ft, two pieces of 39 in.
- Sheathing: 160 sq ft ÷ 32 = 5 sheets of 4 × 8.
Sheathing and nails
Exterior walls are usually sheathed with 7⁄16 in OSB or ½ in plywood in 4 × 8 or 4 × 9 sheets; 4 × 9 sheets cover a 97⅛ in wall plus the rim. Nail schedules (spacing at edges and in the field) come from IRC Table R602.3(1) or the engineer’s shear-wall schedule. For a rough nail estimate, framing a typical wall uses roughly 10–12 framing nails per stud; buy them by the box.
Framing a whole room or house
Run the calculator once per wall and add the results, or treat a simple room as one long wall: the perimeter is the length, and every corner counts. For a 12 × 14 ft room with 8 ft walls, a door and a window:
- Perimeter: 52 ft. Common studs at 16 in O.C.: 624 ÷ 16 = 39, + 1 = 40.
- Openings: a 38 in door and a 3 ft window remove 4 common studs and add 8 kings and jacks: 44.
- Four corners: + 8 = 52 studs, 58 with 10% waste.
- Plates: 52 ft × 3 = 156 lin ft, 12 boards of 16 ft (four per row). The door gap in the bottom plate is cut out after the wall stands.
Interior vs exterior walls
| Exterior wall | Interior partition | |
|---|---|---|
| Studs | 2×4 or 2×6, 16 or 24 in O.C. | 2×4 at 16 or 24 in; 2×3 in some cases |
| Headers | Sized for loads | Single flat 2× if non-bearing |
| Sheathing | OSB or plywood, shear nailing | None |
| Bottom plate | Treated on concrete | Treated on concrete |
Common mistakes
- Forgetting the extra stud at the end of the wall (the “+1”).
- Not counting corners, which need backing for drywall on both walls.
- Using rough opening as door size, or the other way round.
- Buying full 8 ft studs for 8 ft ceilings; precut studs save a cut on every piece.
Notes for framers
Layout. Pull layout from one end so sheet edges land on stud centers: mark 15¼ in, then every 16 in (or 23¼, then every 24).
Advanced framing. 24 in O.C., single top plates with aligned rafters, two-stud corners and right-sized headers can cut lumber use noticeably. Check that your design and code allow it.
Blocking. Count fire blocking, backing for cabinets, grab bars and TV mounts separately; it adds up on interior walls.
Treated plates. Bottom plates on concrete must be pressure-treated (or protected) per code; order them separately.
Tips
- Crown the studs the same way so the wall is flat.
- Frame on the floor and raise the wall, then plumb and brace.
- Pricing lumber? The board foot calculator converts piece prices to board feet.
- Send the list to the yard with WhatsApp or Email under the result.
Frequently asked questions
How many studs do I need for a wall?
Divide the wall length in inches by the stud spacing, round up and add one. A 20 ft wall at 16 in on center needs 240 ÷ 16 = 15, + 1 = 16 studs. Then add 2 studs per corner or wall intersection and 4 per window or door (2 king, 2 jack), and remove the regular studs that would fall inside the openings.
How many studs for a 10 ft wall?
At 16 in on center, 120 ÷ 16 = 7.5, rounded up to 8, + 1 = 9 studs. At 24 in on center, 6 studs. Add extras for corners and openings.
What length studs do I need for an 8 ft wall?
With one bottom plate and a double top plate (4½ in in total), studs for a wall exactly 8 ft tall are 91½ in. Most builders use 92⅝ in precut studs, which make the framed wall 97⅛ in tall, so that 8 ft drywall plus the ceiling drywall fits neatly.
How do I calculate wall plates?
Multiply the wall length by the number of plates: one bottom plate and two top plates makes 3 × the wall length. A 20 ft wall needs 60 lin ft, which is six 16 ft boards (two per row) once you allow for joints.
What is a king stud and a jack stud?
At each side of a window or door, a full-height king stud runs from plate to plate, and a shorter jack (trimmer) stud next to it holds up the header. Cripple studs fill in above the header and below a window sill.
Should studs be 16 or 24 inches apart?
Both are allowed by the IRC in many situations. 16 in on center is standard for load-bearing walls with 2×4s, and gives a stiffer wall. 24 in on center uses fewer studs and suits 2×6 walls and advanced framing. Check your local code and engineer for load-bearing walls.
How many sheets of sheathing for a wall?
Divide the wall area by 32 sq ft per 4 × 8 sheet and round up. A 20 × 8 ft wall is 160 sq ft, so 5 sheets. Many framers sheathe over openings and cut them out later.
How big should a header be?
Header size depends on the opening width, the loads above and the lumber species. IRC tables R602.7 give sizes; a common rule of thumb for small openings is a doubled 2×6 to 2×10 in a load-bearing wall. Non-bearing walls can use a flat 2× header.
Is this framing calculator free to use online?
Yes. The CalcWall Framing Calculator is completely free and works online in any browser, on a phone, tablet or computer. There is nothing to download and no account to create, and the math runs right in your browser, so results appear as you type.