Plywood calculator
How many sheets of plywood or OSB to buy for wall sheathing, a subfloor or a roof, with extra for cuts and the cost.
Buy
26 sheets
- Area to cover
- 746 sq ft
- With extra
- 821 sq ft
- Exact sheets
- 25.64 of 32 sq ft
- Roofing squares
- 7.46
- Cost
- Total weight
- lb
Panel thickness and span rating come from your plans and local code, not from the area. Gable ends and hips need extra pieces; add more extra for them.
How to calculate sheets of plywood
Work out the area to cover in square feet, add extra for cuts, and divide by the area of one sheet. Round up.
- Walls: total wall length × wall height, minus the doors and windows
- Floor: length × width
- Roof: (length + 2 × overhang) × (width + 2 × overhang) × the pitch factor √(1 + (pitch ÷ 12)²), for a gable or hip roof
- Sheets = area × (1 + extra %) ÷ 32 for a 4 × 8 sheet, rounded up
Worked example
Wall sheathing for a 24 × 32 ft house with 8 ft walls: the walls run 2 × (24 + 32) = 112 ft, so 112 × 8 = 896 sq ft, less about 150 sq ft of doors and windows, is 746 sq ft. With 10% extra that's 821 sq ft, ÷ 32 = 25.64, so buy 26 sheets of 4 × 8.
Sheets of plywood by area
With 10% extra for cuts.
| Area | 4 × 8 ft | 4 × 9 ft | 4 × 10 ft |
|---|---|---|---|
| 100 sq ft | 4 | 4 | 3 |
| 250 sq ft | 9 | 8 | 7 |
| 500 sq ft | 18 | 16 | 14 |
| 750 sq ft | 26 | 23 | 21 |
| 1,000 sq ft | 35 | 31 | 28 |
| 1,500 sq ft | 52 | 46 | 42 |
| 2,000 sq ft | 69 | 62 | 55 |
| 3,000 sq ft | 104 | 92 | 83 |
Roof sheathing for common house sizes
Sheets of 4 × 8 for a gable or hip roof with a 12 in overhang all round and 10% extra.
| House | 4/12 | 6/12 | 8/12 | 10/12 | 12/12 |
|---|---|---|---|---|---|
| 24 × 24 ft | 25 | 26 | 28 | 31 | 33 |
| 32 × 24 ft | 33 | 34 | 37 | 40 | 43 |
| 40 × 28 ft | 46 | 49 | 53 | 57 | 62 |
| 50 × 30 ft | 61 | 64 | 69 | 75 | 81 |
| 60 × 32 ft | 77 | 82 | 88 | 95 | 103 |
Plywood questions
How many sheets of plywood do I need?
Divide the square feet you're covering by 32 for 4 × 8 sheets, after adding extra for cuts, and round up. A 24 × 32 ft subfloor is 768 sq ft, so 27 sheets with 10% extra. Walls and roofs need the steps above; choose the job and the calculator does them.
How many sheets of plywood for a roof?
Measure the footprint, add the overhang on every side, and multiply by the pitch factor for the slope. A 24 × 32 ft house with a 6/12 roof and 12 in overhangs has 988 sq ft of roof (9.9 squares), so 34 sheets of 4 × 8 with 10% extra. The table above covers other sizes and pitches; for shingles, use the roofing calculator.
How many square feet are in a sheet of plywood?
4 × 8 ft is 32 sq ft; 4 × 9 ft is 36 sq ft; 4 × 10 ft is 40 sq ft (length × width). Taller sheets let you cover a 9 or 10 ft wall in one piece, top to bottom, with fewer seams.
How much does a sheet of plywood weigh?
It depends on the thickness, the wood, OSB or plywood, and how damp it is, so check the label or ask the supplier. Enter the weight per sheet above to get the total for a delivery or a roof load.
What thickness of plywood do I need?
Sheathing is stamped with a span rating that says how far apart its supports can be. The thickness for your roof, walls or floor depends on that rating, the stud, rafter or joist spacing and your local code, so take it from your plans or ask your building department. The thickness doesn't change how many sheets you need.
Plywood or OSB?
Both come in the same sheet sizes and cover the same area, so the count is the same. For the studs, joists and rafters behind the sheathing, use the framing calculator; for the inside of the walls, the drywall calculator.