Plywood calculator
Measure the walls, or add the areas of a floor, roof or anything else you are covering. You get the sheets to buy with waste, the weight of each sheet from the APA panel tables, and the cost.
Inputs
Result
Plywood and OSB weight per sheet
Approximate weights from the APA Panel Design Specification, Table 6. OSB is about 10% heavier than plywood of the same thickness.
| Thickness | Plywood, lb/sq ft | Plywood 4 x 8 | OSB 4 x 8 |
|---|
How it is worked out
140 ft of 8 ft wall is 1,120 sq ft: 35 sheets of 4 x 8, 39 with 10% waste. In 1/2 in plywood at 1.5 lb per sq ft, each sheet weighs about 48 lb, so the load is close to 1,900 lb.
Which thickness
Structural panels carry an APA span rating, such as 24/16 or 32/16. The left number is the farthest the panel may span between rafters as roof sheathing, the right number between floor joists as subflooring; a single number like 24 oc rates a single-layer floor panel. Common choices:
- Wall sheathing: 7/16 in OSB or 15/32 in plywood rated 24/16, over studs at 16 or 24 in.
- Roof sheathing: 7/16 in for rafters or trusses at 24 in, often with H-clips; 1/2 or 5/8 in under heavy roofing. The roof sheathing calculator works out the pitch and clips.
- Subfloor: 23/32 in tongue-and-groove rated 24 oc over joists at 24 in, or 19/32 in rated 20 oc at 16 to 19.2 in.
Check the span rating on the panel stamp against your framing; the thickness alone is not the rating. For the studs behind the sheathing, use the stud calculator.
Questions
How many sheets of plywood do I need?
Divide the area in square feet by 32 for 4 x 8 sheets and add about 10% for waste. 1,000 sq ft takes 31.25 sheets, so 35 with waste.
How many sheets of plywood for a wall?
Multiply the wall length by its height and divide by 32. A 12 ft wall 8 ft high is 96 sq ft: 3 sheets, set vertically, with the openings cut out of them.
How much does a sheet of 3/4 plywood weigh?
About 74 lb for a 4 x 8 sheet, using the APA's 2.3 lb per sq ft; 23/32 in, the common subfloor thickness, about 70 lb. OSB weighs about 10% more.
How much does a sheet of 1/2 inch plywood weigh?
About 48 lb for 4 x 8, at the APA's 1.5 lb per sq ft. 7/16 in OSB is about 46 lb.
How many square feet does a sheet of plywood cover?
A 4 x 8 sheet covers 32 sq ft, a 4 x 9 sheet 36 and a 4 x 10 sheet 40.
Is OSB or plywood better for sheathing?
Both are rated structural panels and either meets the code at the same span rating. OSB is cheaper and heavier; plywood handles getting wet better and holds nails near the edges better.
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