How many sheets of plywood do I need?
Sheet goods are estimated straight from the area you're covering:
Sheets = area × (1 + waste) ÷ coverage per sheet, rounded up
Multiply length by width for the area, add a waste allowance for cuts and offcuts, and divide by the square footage of one sheet — 32 sq ft for a standard 4 × 8. Round up, because you can't buy a partial sheet. A 20 × 16 ft room is 320 sq ft, which comes to about 11 sheets once waste is included.
Sheet sizes and thicknesses
| Use | Typical panel |
|---|---|
| Subfloor | 3/4 in (23/32) T&G, 32 sq ft |
| Wall & roof sheathing | 7/16–1/2 in OSB/plywood, 32 sq ft |
| Tall walls | 4×9 (36 sq ft) or 4×10 (40 sq ft) |
| Underlayment | 1/4–1/2 in, 32 sq ft |
Tips
- Stagger the seams. Offset end joints row to row for strength — this adds a little waste, so keep 10–15%.
- Leave an expansion gap. Space panels about 1/8 in so they don't buckle; tongue-and-groove edges handle this for you.
- Glue and screw subfloor. Construction adhesive plus screws stops squeaks far better than nails alone.
- Round up by a sheet. One spare panel is cheap insurance against a miscut.