# How many studs do I need?

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.

- Page: https://www.acalculator.org/construction/framing-calculator
- JSON spec: https://www.acalculator.org/construction/framing-calculator.json
- Version: 20f539edf3ca

## Default answer

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.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| l | Wall length | The length of the wall, end to end. |
| oc | Stud spacing | The distance from the center of one stud to the next (on center). |
| open | Doors and windows | How many door and window openings the wall has. |
| po | Extra studs per opening | Studs to add for each opening (king and jack studs). |
| corn | Corners and wall ends | How many corners or wall junctions need extra studs. |
| pc | Extra studs per corner | Studs to add for each corner or junction. |
| top | Top plates | One top plate, or a double top plate as on most load-bearing walls. |
| board | Plate board length | The length of the boards the plates are cut from. |
| waste | Extra for waste | Studs and plates to add, in percent, for bad boards and cutting mistakes. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| buy | Studs to buy | All studs with the extra for waste, rounded up. |
| layout | Studs on the layout | One stud at each spacing from the start of the wall, plus one at the end. |
| studs | Studs before waste | The layout studs plus the extras for openings and corners. |
| plateLength | Plate length | The wall length × (1 bottom plate + the top plates). |
| boards | Plate boards to buy | The plate length with the extra for waste ÷ the board length, rounded up. |

## 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⌉.

## Assumptions

- 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.

## Worked examples

1. l = 6.096, oc = 16, open = 1, po = 2, corn = 0, pc = 2, top = 2, board = 8, waste = 10% gives layout = 16, studs = 18, buy = 20, boards = 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. l = 2.4384, oc = 16, open = 0, po = 2, corn = 0, pc = 2, top = 2, board = 8, waste = 0% gives layout = 7, buy = 7, boards = 3, plateLength = 7.3152. Source: IRC 2021 R602.3 (16 in on center).
3. l = 6, oc = 600, open = 0, po = 2, corn = 2, pc = 2, top = 2, board = 3.6, waste = 10% gives layout = 11, studs = 15, buy = 17, boards = 6. Source: IRC 2021 R602.3 (on-center spacing).

## FAQ

### 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.

## Sources

- International Code Council, 2018 International Residential Code, Chapter 6, section R602.3 and Table R602.3(5), Size, height and spacing of wood studs (16 and 24 in on center; the 2021 edition keeps the table), retrieved 2026-10-01. https://codes.iccsafe.org/content/IRC2018P4/chapter-6-wall-construction
- International Code Council, 2021 International Residential Code, section R602.3.2, Top plate (double top plate). https://codes.iccsafe.org/s/IRC2021P3/chapter-6-wall-construction/IRC2021P3-Pt03-Ch06-SecR602.3.2