Plywood Calculator
How many sheets of plywood or OSB for a floor, the walls of a building, a roof, or any area, with waste and cost.
Sheets to buy
7sheets
- Area
- 192 ft²
- Exact sheets
- 6
- Cost
- $266.00
Lay floor and roof sheets with the long edge across the joists or rafters and stagger the end joints by at least one framing bay.
Recommended panel thickness
| Use | Framing spacing | Common panel |
|---|---|---|
| Subfloor (T&G) | 16" o.c. | 23/32" (¾") plywood or OSB, 24 oc rated |
| Subfloor (T&G) | 24" o.c. | 7/8" or 1-1/8" |
| Roof sheathing | 16" o.c. | 7/16" OSB or 15/32" plywood |
| Roof sheathing | 24" o.c. | 7/16" (24/16) with H-clips, or 19/32" in snow country |
| Wall sheathing | 16" or 24" o.c. | 7/16" OSB or 15/32" plywood |
| Shop cabinets / shelves | n/a | ¾" hardwood plywood (Baltic birch for drawers: ½") |
Check the APA span-rating stamp on the panel and your local code; high-wind and seismic zones have their own sheathing rules.
Ask the shop
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Questions people ask
How many sheets of plywood do I need?
Work out the area to cover in square feet and divide by the area of one sheet: a 4×8 sheet is 32 sq ft, a 4×10 is 40 sq ft. Add 10% for cuts and waste (15% on roofs with hips and valleys), then round up. A 12 × 16 ft floor is 192 sq ft ÷ 32 = 6 sheets, 7 with waste.
How many sheets of plywood for a roof?
Multiply the building footprint including overhangs by the rafter factor for the pitch (1.118 for 6/12), divide by 32 and add 10–15%. A 30 × 40 ft house with 1 ft overhangs and a 6/12 roof: 32 × 42 × 1.118 = 1,503 sq ft, or 47 sheets, 52–54 with waste.
What thickness plywood for a subfloor?
With joists at 16" on center, use 23/32" (nominal ¾") tongue-and-groove plywood or OSB rated 24" o.c.; many builders use it at 16" as well for a stiffer floor. At 24" joist spacing, use 7/8" or 1-1/8" panels. Look for the span rating stamp, e.g. "24 oc".
What thickness plywood for roof sheathing?
For rafters or trusses at 24" on center, 7/16" OSB or 15/32" plywood rated 24/16 is the common minimum under shingles; use H-clips between rafters on unsupported edges. Heavy snow areas often step up to 19/32" or 5/8".
How do I account for windows and doors on walls?
Subtract large openings (garage doors, big windows) from the wall area, but not small ones: offcuts around small windows are rarely reusable. Many framers simply sheath through all openings and cut them out afterward, then subtract only half the opening area when estimating.