Plywood Calculator
Sheet count for subfloor, wall sheathing and roof decking. Enter the area’s length and width; for a roof, enter the footprint and pick the pitch and the calculator scales the area up the slope. A 4 × 8 sheet is 32 ft² — 10% waste covers cuts and stagger.
Order 14 sheets — units of 4 × 8 sheeting are 50 per lift; sheets are cheaper by the unit.
- Area
- 384 ft²
- Waste / cuts 10%
- + 38 ft²
- Coverage to buy
- 422 ft²
- Metric
- 35.7 m²
- 4 × 8 ft sheets (32 ft²)
- 14
- 4 × 10 ft sheets (40 ft²)
- 11
- Approx. weight
- 700 lb
- Nails / screws, 8d ring shank
- 2 lb
- Materials + delivery$18–$65 / sheet · Sep 2026
- $327 – $985
- Installed (with labor)typ. $1,195
- $711 – $2,137
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What will this plywood & osb job cost?
See the installed price range for these quantities and get up to 3 quotes from local contractors. Free, no obligation.
How to calculate plywood or OSB by hand
Sheets = Area (ft²) × pitch factor × (1 + waste) ÷ 32
Worked example
- Area: 24 ft × 16 ft = 384 ft² (a flat floor — pitch factor 1).
- Waste 10%: 384 × 1.10 = 422 ft².
- Sheets: 422 ÷ 32 = 13.2 → 14 sheets of 4 × 8.
- For a 6/12 roof over the same footprint: 384 × 1.118 = 429 ft² per side → 15 sheets per plane.
- 4 × 8 sheet
- 32 ft²
- 4 × 10 sheet
- 40 ft²
- Sheets per 100 ft², 10% waste
- 3.4
- Pitch factor 6/12 · 8/12 · 12/12
- 1.118 · 1.202 · 1.414
Questions crews ask
How many sheets of plywood do I need?
Divide the area by 32 ft² per 4 × 8 sheet and add 10% for cuts: a 24 × 16 ft floor is 384 ft² → 14 sheets. For roofs multiply the footprint by the pitch factor first (1.118 for 6/12) and do each plane.
How many sheets of plywood for a 24x24 garage floor?
576 ft² ÷ 32 = 18 sheets, 20 with 10% waste. Use ¾″ tongue-and-groove for a subfloor over joists at 16″ centres; 23/32 OSB is the budget equivalent.
What is the roof pitch factor?
The multiplier that converts footprint to sloped area: √(rise² + 12²) ÷ 12. A 4/12 roof is 1.054, 6/12 is 1.118, 8/12 is 1.202, 12/12 is 1.414. Multiply the flat footprint of each roof plane by the factor.
Plywood or OSB for sheathing?
OSB is 20–40% cheaper and fine for walls and roofs under a dry roof. Plywood holds up better if it gets wet before dry-in, holds nails a little better and is lighter. For subfloor use tongue-and-groove ¾″ of either, glued and screwed.
How much does a sheet of plywood weigh?
Roughly 1.5 lb per ft² per ½″ of thickness: a ½″ 4 × 8 sheet is 45–50 lb, ¾″ about 70 lb. OSB is slightly heavier than plywood of the same thickness.