Wall Stud Calculator

Wall stud calculator: studs and plate lumber from wall length

A wall stud calculator spaces vertical studs along the wall, adds a framing allowance, and totals the plate lumber. The count per wall is ⌈wall length in inches ÷ spacing⌉ + 1, so a wall that is not an exact multiple of the spacing still gets a stud at the far end. A 20 ft wall at 16 inches on center has 16 studs, and the calculator raises the total by 15 percent for corners and openings to 19.

Plates are the horizontal boards at the bottom and top of the wall. With a single bottom plate and a doubled top plate, a 20 ft wall needs 60 linear feet of plate stock.

The formula in plain words

Picture a row of fence posts along the wall, one every 16 inches. Start with a post at one end. Keep placing posts until you run out of wall. If the last gap is short, you still put a post at the very end.

• Studs per wall = ⌈(wall length × 12) ÷ spacing⌉ + 1
• Total studs = studs per wall × number of walls × 1.15, rounded up
• Plate linear feet = wall length × plate rows × number of walls

The “+ 1” is the stud at the starting end. The 15 percent covers corners, intersections, and the king, jack, and cripple studs around openings.

Worked examples

1. Single wall, 20 ft long, 16 in OC, 3 plate rows

• Studs: ⌈240 ÷ 16⌉ + 1 = 15 + 1 = 16
• Total: 16 × 1.15 = 18.4, rounded up to 19 studs
• Plates: 20 × 3 = 60 linear feet

2. Four walls of 12 ft, 24 in OC, 3 plate rows

• Studs per wall: ⌈144 ÷ 24⌉ + 1 = 7
• Total: 7 × 4 × 1.15 = 32.2, rounded up to 33 studs
• Plates: 12 × 3 × 4 = 144 linear feet

In example 2, wider spacing cut the count a lot. At 16 inches the same four walls would need ⌈144 ÷ 16⌉ + 1 = 10 studs each, and 10 × 4 × 1.15 = 46 studs.

Studs per wall by length and spacing

These are the base counts before the 15 percent allowance. A 10 ft wall at 16 in OC (7.5 spaces) and a 30 ft wall (22.5 spaces) round up, so each gets an end stud and a short last bay.

Wall length	At 16 in OC	At 24 in OC
8 ft	7	5
10 ft	9	6
12 ft	10	7
20 ft	16	11
30 ft	24	16

How to measure

• Wall length: Measure along the plate line from one end to the other, not along the finished drywall.
• Count the openings: List every door and window. Walls with many openings need more than the 15 percent allowance.
• Corners and tees: Each corner and wall intersection uses extra studs for nailing surfaces.
• Wall height: Decide stud length from the ceiling height minus the plates.
• Spacing: Take it from your plans, because load-bearing walls may be required to be closer.

Common mistakes

• Forgetting the end stud. Dividing length by spacing gives gaps, not studs.
• Trusting the allowance for a heavily cut-up wall. A wall with large windows and doors uses far more king and jack studs than the average.
• Mixing feet and inches. The formula converts the wall to inches first, so enter length in feet.
• Overlooking plate laps. Plates are bought in fixed lengths, so a long wall needs joints staggered along it.
• Leaving out blocking and fire stops. Horizontal blocking is separate lumber that this count does not include.

Turning the count into a lumber order

The 20 ft wall needs 19 studs and 60 linear feet of plate stock. Plates can be bought in 10 ft boards, which means six boards for this wall. Stagger the joints so the doubled top plate laps across the seams below it.

Order the studs a few at a time if you can. Some lumber arrives crooked or split, and the 15 percent allowance gives you room to cull the worst pieces without a second trip.

Related calculators

Once the wall is framed, sheet it with the drywall calculator. For sheathing, use the plywood calculator. The board foot calculator prices lumber by volume, and the framing calculator covers other framing members.