Framing Calculator

How many studs and plates you need

A framing calculator turns wall length and stud spacing into a lumber list. Convert the wall length to inches, divide by the spacing, round up, and add one stud for the far end. Then add 15% for corners and openings. Studs per wall = ⌈length in ÷ spacing⌉ + 1. Total studs = ⌈studs per wall × walls × 1.15⌉. Plate feet = length × plate rows × walls. Four 20 ft walls at 16 inches on center need 74 studs and 240 ft of plate.

Run it once for each group of walls that share a length. Add the results for the whole building.

Why the formula looks like this

Picture the bottom plate with a mark every 16 inches. Along 240 inches there are 15 full gaps. Fifteen gaps need sixteen studs, one at each end of every gap. That is the “+1”. When the wall is not an exact multiple of the spacing, the last gap is shorter and still gets its end stud.

Real walls need more than the evenly spaced studs:

• Corners take two or three extra studs so both walls have nailing for drywall.
• Wall intersections need backing where an interior wall meets an exterior one.
• Each door or window adds king studs, jack (trimmer) studs, and short cripples above and below.

The 15% allowance covers a typical mix of these.

Worked examples

Example 1: Four walls of a 20 × 20 ft shed or room, 16 in spacing, 3 plates

• Studs per wall: ⌈240 ÷ 16⌉ + 1 = 15 + 1 = 16
• Total studs: 16 × 4 × 1.15 = 73.6, rounded up to 74
• Plate lumber: 20 × 3 × 4 = 240 linear ft, or 15 boards of 16 ft

Example 2: Single partition wall, 12 ft long, 24 in spacing, 3 plates

• Studs per wall: ⌈144 ÷ 24⌉ + 1 = 6 + 1 = 7
• Total studs: 7 × 1 × 1.15 = 8.05, rounded up to 9
• Plate lumber: 12 × 3 × 1 = 36 linear ft

Example 3: Garage side walls, two walls of 24 ft, 16 in spacing

• Studs per wall: ⌈288 ÷ 16⌉ + 1 = 19
• Total studs: 19 × 2 × 1.15 = 43.7, so 44
• Plates: 24 × 3 × 2 = 144 ft

Stud counts for a 20 ft wall

Spacing	Studs per wall	4 walls with 15%	Plate ft (4 walls)
12 in	21	97	240
16 in	16	74	240
24 in	11	51	240

Precut stud lengths

Finished ceiling	Common precut stud	With 3 plates (1½ in each)
8 ft	92⅝ in	about 97⅛ in of wall height
9 ft	104⅝ in	about 109⅛ in
10 ft	116⅝ in	about 121⅛ in

Precuts let a standard 8 ft wall take full drywall sheets with room for the ceiling board.

How to measure

1. Measure each wall along the floor from outside corner to outside corner, or to the face of the wall it meets.
2. Group walls of the same length and spacing.
3. Count openings per wall. If a wall has more than two or three, add a few studs beyond the 15%.
4. Check the plate rows. Use 3 for a standard wall, 2 for a single top plate where permitted, and 4 if you add a sill plate on concrete.

Common mistakes

• Rounding down before adding the end stud. A wall that is not an exact multiple of the spacing would end with no stud at the far corner.
• Forgetting the doubled top plate. Three rows, not two, on most walls.
• Ordering plates in exact lengths. Joints in the top plates must be staggered, so long boards waste less.
• Ignoring headers. They often need 2×8 to 2×12 stock that is not in the stud count.

Related calculators

The stud calculator handles a single wall in more detail. Price the lumber with the board foot calculator, estimate the job with the framing cost calculator, and sheet the finished walls with the drywall calculator.

Framing is structural. Verify stud size, spacing, and headers against local code, and have load-bearing changes reviewed by a licensed professional.