Plywood Calculator
Count the sheets of plywood or OSB needed to cover an area.
What you'll need to order
- plywood or OSB sheets
- construction screws
- construction adhesive
- H-clips
Prices vary by region and haul distance. Get quotes from at least two local suppliers.
How this calculator works
sheets = area ÷ 32 × (1 + waste ÷ 100)
A standard 4 by 8 sheet covers 32 sq ft. Sheets sold as 4x9 or 4x10 cover 36 and 40 sq ft — useful on tall walls where they eliminate a horizontal joint entirely.
Switch the site to metric — the control is in the footer — and your inputs, your results and the tables below follow. The formula, the constants, the guidance text and the sources stay in US units on purpose: that is how the standards they come from are written, and restating them would detach each figure from the document you are meant to be able to check it against.
Where these numbers come from
- US Dept. of Commerce Voluntary Product Standard PS 1 (Structural Plywood) 2019 — standard structural panel dimensions, from which the 32 sq ft per sheet follows
Check the edition. Codes are amended every few years, and the one your inspector works from may not be the one named above.
Worked example
With area length 24 ft, area width 16 ft, waste allowance 10 , this calculator returns 13.2 .
Waste allowance
The headline figure includes a 10% allowance for waste and over-ordering. The exact requirement is shown alongside it.
Plywood sheets by area
Figures below assume area width 16 ft × waste allowance 10 . Each row is a link that fills in the calculator above. Send one and the other end sees the same figures you do.
| Area length | Sheets needed (4x8) | Area to cover (sq ft) |
|---|---|---|
| 8 ft | 4.40 | 128.0 |
| 12 ft | 6.60 | 192.0 |
| 16 ft | 8.80 | 256.0 |
| 24 ft | 13.20 | 384.0 |
| 32 ft | 17.60 | 512.0 |
| 48 ft | 26.40 | 768.0 |
Areas 16 ft wide, with a 10% waste allowance. A standard 4x8 ft sheet covers 32 square feet.
How much plywood for a floor, roof or wall?
Every row here opens the calculator already filled in. Copy that link and the numbers travel with it.
| Job | Size | Sheets needed (4x8) |
|---|---|---|
| Shed floor | 12 ft × 10 ft × 10 | 4.13 |
| Room subfloor | 16 ft × 12 ft × 10 | 6.60 |
| Garage roof deck | 24 ft × 16 ft × 12 | 13.44 |
| Whole house sheathing | 140 ft × 9 ft × 15 | 45.28 |
| Basement wall lining | 60 ft × 8 ft × 10 | 16.50 |
Waste rises with the number of cuts. Ten percent is right for a simple rectangle, 15% once there are openings, angles or a cut-up roof.
Plywood thickness by use
| Type | Thickness (in) | Notes |
|---|---|---|
| Roof sheathing, 24 in rafters | 0.50 | 15/32 in nominal; the common case |
| Wall sheathing | 0.50 | 7/16 in OSB is the usual substitute |
| Subfloor, 16 in joists | 0.75 | 23/32 in tongue and groove |
| Subfloor, 24 in joists | 1.13 | Or double-layer 3/4 in |
| Cabinet and furniture grade | 0.75 | Hardwood-faced, sanded both sides |
| Underlayment | 0.25 | Over an existing subfloor only |
Nominal thickness is always more than actual — a "3/4 inch" sheet measures 23/32. That difference matters when it meets flooring or trim.
Frequently asked questions
How many sheets of plywood do I need?
Divide the area in square feet by 32, then add 10 to 15% for waste. A 16 by 12 ft room is 192 sq ft, so seven sheets with waste.
How much does a sheet of plywood cost?
$25 to $60 for construction-grade 4x8 sheets depending on thickness, and $60 to $150 for hardwood-faced cabinet grade. Prices move sharply with lumber markets.
How much does a sheet of plywood weigh?
About 40 lb for 1/2 inch, 60 lb for 3/4 inch, and 70 lb for 3/4 inch tongue and groove subfloor. Worth knowing before planning a solo installation.
How many square feet is a sheet of plywood?
Thirty-two, for the standard 4 by 8 sheet. Divide your area by 32 for the raw count, then add waste for cuts around openings and at the edges.
What thickness plywood do I need?
Half inch for wall sheathing, 5/8 for roof decking at 24 inch rafter spacing, and 3/4 tongue-and-groove for subfloor. Thinner panels save little and sag noticeably.
Is OSB as good as plywood?
Structurally they are rated the same and code treats them interchangeably. Plywood recovers better from getting wet, while OSB swells permanently at the edges — which matters most during construction.
Which way should sheathing run?
Perpendicular to the framing, with the long dimension crossing the studs, joists or rafters. This spans the most supports and gives the strongest assembly. Stagger the joints between rows.