# How many plywood sheets?

Plywood calculator: how many 4 × 8 ft (or other) sheets of plywood or OSB cover a subfloor, wall or pitched roof deck, with waste and cost.

- Page: https://www.acalculator.org/construction/plywood-calculator
- JSON spec: https://www.acalculator.org/construction/plywood-calculator.json
- Version: 619ca1424786

## Default answer

Example with the default inputs (Surface Floor or wall, Length 24 ft, Width 16 ft, Sheet size 4 × 8 ft, Waste 10%): Sheets of plywood to buy: 14, for 384 ft².

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| s | Surface | A flat floor or wall, or a pitched roof measured in plan. |
| l | Length | The length of the floor or wall, or of the roof in plan with its overhangs. |
| w | Width | The width of the floor, the height of the wall, or the roof’s width in plan. |
| pitch | Roof pitch, rise in 12 | Inches the roof rises for each 12 in of run, such as 6 for a 6/12 roof. |
| sh | Sheet size | The size of one sheet. |
| sl | Sheet length | The length of one sheet. |
| sw | Sheet width | The width of one sheet. |
| x | Waste | Extra for cuts, in percent. |
| p | Price per sheet | The price of one sheet. Leave empty to skip the cost. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| sheets | Sheets to buy | Area × (1 + waste) ÷ sheet area, rounded up. |
| area | Area to cover | Length × width, × the roof slope factor for a roof. |
| exactSheets | Sheets without waste | Area ÷ sheet area, before rounding. |
| factor | Roof slope factor | √(1 + (rise ÷ 12)²); 1 for a floor or wall. |
| cost | Cost | Sheets to buy × the price per sheet. |

## Method

Sheets = length × width × slope factor × (1 + waste ÷ 100) ÷ sheet area, rounded up; slope factor = √(1 + (pitch ÷ 12)²) for a roof, 1 otherwise.

## Assumptions

- Offcuts are reused where they fit, so sheets are counted by area; waste covers what cannot be reused.
- A roof is measured in plan (from above), overhangs included; the slope factor turns that into the sloped area.
- Openings are not taken away; subtract them from the length or width if they are large.

## Worked examples

1. s = flat, l = 7.3152, w = 4.8768, sh = 4x8, x = 10%, p = $45.00 gives sheets = 14, exactSheets = 12, cost = $630.00. Source: Wikipedia, Plywood (the most commonly used sheets are 4 by 8 ft, 1,220 × 2,440 mm; 1,200 × 2,400 mm is a common metric size; 5 × 5 ft is common for Baltic birch), https://en.wikipedia.org/wiki/Plywood (retrieved 2026-10-03).
2. s = roof, l = 12.192, w = 9.144, pitch = 9, sh = 4x8, x = 0% gives factor = 1.25, area = 139.35456, sheets = 47. Source: Wikipedia, Plywood (the most commonly used sheets are 4 by 8 ft, 1,220 × 2,440 mm; 1,200 × 2,400 mm is a common metric size; 5 × 5 ft is common for Baltic birch), https://en.wikipedia.org/wiki/Plywood (retrieved 2026-10-03).
3. s = flat, l = 4.8, w = 2.4, sh = metric, x = 0% gives sheets = 4, exactSheets = 4. Source: Wikipedia, Plywood (the most commonly used sheets are 4 by 8 ft, 1,220 × 2,440 mm; 1,200 × 2,400 mm is a common metric size; 5 × 5 ft is common for Baltic birch), https://en.wikipedia.org/wiki/Plywood (retrieved 2026-10-03).
4. s = roof, l = 12.192, w = 9.144, pitch = 6, sh = 4x8, x = 10% gives factor = 1.118034, sheets = 47. Source: Wikipedia, Plywood (the most commonly used sheets are 4 by 8 ft, 1,220 × 2,440 mm; 1,200 × 2,400 mm is a common metric size; 5 × 5 ft is common for Baltic birch), https://en.wikipedia.org/wiki/Plywood (retrieved 2026-10-03).

## FAQ

### How many sheets of plywood do I need?

Divide the area by the area of one sheet, add waste for cuts, and round up. A 24 × 16 ft floor is 384 ft²; 384 ÷ 32 = 12 sheets of 4 × 8, or 14 with 10% waste.

### How many square feet is a sheet of plywood?

A 4 × 8 ft sheet covers 32 ft². A 4 × 9 ft sheet covers 36 ft², a 4 × 10 ft sheet 40 ft², and a 5 × 5 ft sheet 25 ft². A metric 1,200 × 2,400 mm sheet covers 2.88 m².

### How do I work out plywood for a roof?

Measure the roof from above (its plan, with overhangs) and multiply by the slope factor √(1 + (pitch ÷ 12)²). A 9/12 roof has a factor of 1.25, so a 40 × 30 ft plan is 1,500 ft² of roof deck, 46.9 sheets, so 47.

### Does this work for OSB?

Yes. OSB is sold in the same sheet sizes as plywood, so the count is the same.

### How much waste should I add?

About 10% covers cuts at edges and around openings for a simple floor or wall. Use more for a roof with hips and valleys or a room with many corners.

### Should I take out windows and doors?

For wall sheathing, small openings are usually sheathed over and cut out, so leave them in. Take out large openings by shortening the length you type.

## Sources

- Wikipedia, Plywood: the most commonly used sheets are 4 by 8 ft (1,220 × 2,440 mm); 1,200 × 2,400 mm is a common metric size; 5 × 5 ft is common for Baltic birch, retrieved 2026-10-03. https://en.wikipedia.org/wiki/Plywood
- NIST Special Publication 811 (2008), Appendix B: 1 ft = 0.3048 m exactly, 1 ft² = 0.09290304 m², retrieved 2026-10-03. https://www.nist.gov/pml/special-publication-811