acalculator

How many studs do I need?

Type the wall length and pick the stud spacing. The stud calculator lays out one stud per spacing, adds studs for openings and corners and a waste allowance, and counts the plate boards.

Your numbers

Units
Top plates
Studs to buy
20

A 20 ft wall needs 18 studs, 20 with waste, and 9 plate boards.

Studs on the layout
16
Studs before waste
18
Plate length
60 ft
Plate boards to buy
9

Studs to buy: 20. A 20 ft wall needs 18 studs, 20 with waste, and 9 plate boards.

How to calculate

A stud calculator for wall framing: the studs for a wall at 12, 16, 19.2 or 24 in on center (or 400 and 600 mm), with extras for openings and corners, waste, and the plate boards.

Example with the default inputs (Wall length 20 ft, Stud spacing 16 in, Doors and windows 1, Extra studs per opening 2, Corners and wall ends 0, Extra studs per corner 2, Top plates Double, Plate board length 8 ft, Extra for waste 10%): A 20 ft wall needs 18 studs, 20 with waste, and 9 plate boards.

Method: Layout studs = ⌈wall length ÷ spacing⌉ + 1; studs = layout + openings × extra per opening + corners × extra per corner; to buy = ⌈studs × (1 + waste ÷ 100)⌉; plate boards = ⌈wall length × (1 + top plates) × (1 + waste ÷ 100) ÷ board length⌉.

  • One straight wall with a stud at each spacing from one end and one at the other end.
  • By default 2 extra studs per opening and 2 per corner, an estimating allowance and not a code rule; set your own counts for your framing.
  • One bottom plate and a single or double top plate; headers, cripples, blocking and sheathing are not counted.
  • Waste is 10% by default.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Wall length 20 ft, Stud spacing 16 in, Doors and windows 1, Extra studs per opening 2, Corners and wall ends 0, Extra studs per corner 2, Top plates Double, Plate board length 8 ft, Extra for waste 10% gives Studs on the layout 16, Studs before waste 18, Studs to buy 20, Plate boards to buy 9.Source: IRC 2021 R602.3 and Table R602.3(5), stud spacing 16 or 24 in on center; R602.3.2 double top plate (https://codes.iccsafe.org/s/IRC2021P3/chapter-6-wall-construction/IRC2021P3-Pt03-Ch06-SecR602.3.2)
  2. Wall length 8 ft, Stud spacing 16 in, Doors and windows 0, Extra studs per opening 2, Corners and wall ends 0, Extra studs per corner 2, Top plates Double, Plate board length 8 ft, Extra for waste 0% gives Studs on the layout 7, Studs to buy 7, Plate boards to buy 3, Plate length 24 ft.Source: IRC 2021 R602.3 (16 in on center)
  3. Wall length 19.69 ft, Stud spacing 600 mm, Doors and windows 0, Extra studs per opening 2, Corners and wall ends 2, Extra studs per corner 2, Top plates Double, Plate board length 3.6 m, Extra for waste 10% gives Studs on the layout 11, Studs before waste 15, Studs to buy 17, Plate boards to buy 6.Source: IRC 2021 R602.3 (on-center spacing)

How it works

With L the wall length and s the on-center spacing:

  • Studs on the layout = ⌈L ÷ s⌉ + 1: one stud at the start and at every spacing, and one at the end.
  • Studs before waste = layout studs + openings × extra studs per opening + corners × extra studs per corner.
  • Studs to buy = ⌈studs before waste × (1 + waste ÷ 100)⌉.
  • Plate length = L × (1 + top plates): one bottom plate and one or two top plates.
  • Plate boards to buy = ⌈plate length × (1 + waste ÷ 100) ÷ board length⌉.

⌈x⌉ means x rounded up to a whole number. The plate length shows to 2 decimals, in feet (US) or metres (Metric), rounded half up.

Exact arithmetic. The wall length is read as the exact decimal you typed, in the unit you typed it in (a feet-and-inches pair counts by its value in inches), and the spacings and board lengths are exact (16 in = 0.4064 m, 600 mm = 0.6 m, 8 ft = 2.4384 m). Every step is exact, so an 8 ft wall at 16 in is exactly 6 spacings and 7 studs, not 8.

Spacings: 12, 16, 19.2 and 24 in; 400 and 600 mm. Boards: 8, 10, 12 and 16 ft; 2.4, 3.6 and 4.8 m.

Assumptions

  • One straight wall, with studs from end to end at the chosen spacing.
  • 2 extra studs per opening and 2 per corner by default: an estimating allowance, not a code rule. Set your own counts.
  • Waste is 10% by default.
  • Headers, cripples, blocking and sheathing are not counted.

Rules

  • The wall length is more than 0 and at most 1,000 m.
  • Openings, corners and the extras per opening and per corner are whole numbers from 0 to 100; waste is 0% to 100%.

Worked examples by hand

A 20 ft wall at 16 in with one opening. 240 ÷ 16 = 15, so 15 + 1 = 16 layout studs; + 2 for the opening = 18; × 1.1 = 19.8, so buy 20. Plates: 20 × 3 = 60 ft; × 1.1 = 66 ÷ 8 = 8.25, so 9 boards of 8 ft.

An 8 ft wall at 16 in, no extras, no waste. 96 ÷ 16 = 6 exactly, so 7 studs. Plates: 8 × 3 = 24 ft = 7.3152 m, exactly 3 boards of 8 ft.

A 6 m wall at 600 mm with two corners. 6,000 ÷ 600 = 10, so 11 layout studs; + 4 for the corners = 15; × 1.1 = 16.5, so buy 17. Plates: 18 m × 1.1 = 19.8 ÷ 3.6 = 5.5, so 6 boards of 3.6 m.

Other questions people ask

How many studs do I need for a wall?

Divide the wall length by the stud spacing, round up, and add 1 for the end. A 20 ft (240 in) wall at 16 in on center needs 240 ÷ 16 = 15, + 1 = 16 studs, before extras for openings, corners and waste.

Is it one stud per foot?

That is a quick rule of thumb for 16 in spacing: it lands close to the layout count plus the usual extras. The calculator counts the layout exactly and lets you set the extras: a 20 ft wall gives 16 layout studs, 18 with one opening, and 20 with 10% waste.

What stud spacing should I use?

Most house walls are framed at 16 in on center; 24 in is common for 2×6 walls and allowed by the IRC within its height limits (Table R602.3(5)). Metric walls usually use 400 or 600 mm. Check your local code and your sheathing.

How many extra studs for a door or window?

Each opening needs king studs, jack studs and cripples, but the studs that would have stood in the opening are not needed. Builders often allow about 2 extra studs per opening and 2 per corner, which are the defaults here. Change them to match your plan.

How many plates does a wall need?

One bottom (sole) plate and, on most load-bearing walls, a double top plate (IRC R602.3.2). For a 20 ft wall that is 60 ft of plate, or 9 eight-foot boards with 10% waste.

Does the count include headers and blocking?

No. Headers, cripples, fire blocking and sheathing depend on the opening sizes and the plan, so add them separately.