Stud Calculator
Estimate how many wall studs and plate boards you need for a framed wall. Enter the wall length and stud spacing, add corners, intersecting walls and openings, and the calculator adds a waste allowance and shows the working.
Add the lengths of all walls framed the same way.
Each corner adds 2 studs.
Where another wall meets this one: 2 studs each.
Each opening adds 2 jack studs.
For culls, cripples and blocking. 10-15% is common.
How to use the Stud Calculator
- Enter the wall length in feet. For several walls framed the same way, add their lengths together.
- Pick the stud spacing: 16 in on center is standard for most walls, 24 in for many exterior walls built with advanced framing.
- Add corners, intersections and openings so the calculator includes the extra studs they need.
- Choose single or double top plate, the plate board length and a waste allowance.
- Read the results: studs to buy, plate boards and optional cost, then compare other spacings in the table.
How the stud count is calculated
Layout studs = ⌈wall length (ft) × 12 ÷ spacing (in)⌉ + 1. The "+1" is the stud that closes the end of the wall.
Extras: about 2 studs for each corner (to give backing for drywall on the inside corner), 2 for each place where another wall meets this one (a T-intersection), and 2 for each door or window (jack studs). King studs and cripples are usually made from the layout studs that would have fallen inside the opening.
Waste: multiply by your waste allowance and round up. Example, a 20 ft wall at 16 in on center with 2 corners and 1 door: ⌈20 × 12 ÷ 16⌉ + 1 = 16 layout studs, + 2×2 + 2×1 = 6 extras = 22, + 10% (3) = 25 studs.
Plates: one bottom plate plus one or two top plates. Linear feet = wall length × (1 + top plates). A 20 ft wall with a double top plate needs 60 ft of plate, 66 ft with 10% waste, which is 6 boards of 12 ft.
Studs needed by wall length
Layout studs only (before corners, openings and waste).
| Wall length | 12 in O.C. | 16 in O.C. | 24 in O.C. |
|---|---|---|---|
| 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
| Wall height | Precut stud | Framed height (1 bottom + 2 top plates) |
|---|---|---|
| 8 ft | 92-5/8 in | 97-1/8 in |
| 9 ft | 104-5/8 in | 109-1/8 in |
| 10 ft | 116-5/8 in | 121-1/8 in |
Nominal 2x4 and 2x6 lumber is actually 1-1/2 in thick, which is why each plate takes 1.5 in of the wall height. Always check the framing details your local building code requires, especially for load-bearing and exterior walls.
Frequently asked questions
How many studs do I need for a wall?
For studs 16 inches on center, multiply the wall length in feet by 0.75 and add 1 (12 ÷ 16 = 0.75). A 20 ft wall needs 20 × 0.75 + 1 = 16 layout studs. Add about 2 studs per corner, wall intersection and opening, then 10-15% for waste.
What is the rule of thumb for studs per foot?
A common shortcut is one stud per foot of wall at 16 in on center. It roughly covers layout studs plus the extras for corners and openings, but counting them separately as this calculator does is more accurate.
Should I use 16 or 24 inch stud spacing?
16 inches on center is standard for interior walls and most load-bearing walls. 24 inches on center uses fewer studs and leaves more room for insulation, and is allowed by building codes for many walls with 2x6 studs or single-story loads. Check your local code and the sheathing or drywall requirements.
How many plates does a wall have?
A typical wall has one bottom (sole) plate and a double top plate, so you need 3 times the wall length in plate lumber. Some non-load-bearing walls and advanced framing use a single top plate (2 times the wall length).
What size studs do I buy for an 8 foot wall?
Precut studs of 92-5/8 inches are made for 8 ft walls with one bottom and two top plates: 92-5/8 + 3 × 1-1/2 = 97-1/8 inches, which leaves room for 8 ft drywall and the ceiling drywall. For 9 ft and 10 ft walls the precut sizes are 104-5/8 and 116-5/8 inches.
Why add extra studs for doors and windows?
Each opening needs a king stud and a jack (trimmer) stud on each side, plus short cripple studs above the header and below a window sill. The layout studs that fall inside the opening are usually cut down for cripples, so adding about 2 studs per opening is a good estimate.
How much waste should I allow for framing lumber?
10% is a common allowance for crooked or split boards, blocking and fire blocking. Use 15% for complicated walls with many openings or if the lumber quality is poor.