Plywood Calculator
Sheet count for plywood, OSB, MDF or any sheet good covering a rectangular area — 4×8, 4×10 or 4×12 panels with waste factor.
Calculation results
Sheets needed
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sheets
Net project area
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ft²
Adjusted area (with waste)
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ft²
Estimated cost
$
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Sheet count rounds up to whole panels. For complex layouts, buy one extra sheet for sacrificial cuts and pattern matching.
Informational only. Sheet-good thickness affects span tables — choose ½″ to ¾″ for subfloors, ⅜″ to ½″ for wall sheathing, ¼″ for cabinet backs. Always verify thickness with your local code or engineer for structural applications.
Understanding the formula
area = length × width · adjusted = area × (1 + waste / 100)
sheets = ⌈ adjusted ÷ sheet_area ⌉
The calculation is straightforward — multiply length by width to get the project area, apply the waste factor, divide by the area each sheet covers, and round up. The waste factor accounts for the cuts that fall off panel edges, off-cuts that are too small to use elsewhere, and the inevitable mis-cut.
Worked example — 16 × 24 ft subfloor in 4×8 sheets
- Net area = 16 × 24 = 384 ft²
- Adjusted (10 % waste) = 384 × 1.10 = 422 ft²
- Sheets = ⌈ 422 ÷ 32 ⌉ = ⌈ 13.2 ⌉ = 14 sheets
At a Big-Box price of about $32 per 4×8 ¾″ CDX (2026), that subfloor is roughly $450 of plywood.
Plywood thickness reference
| Thickness | Typical use | Notes |
|---|---|---|
| ¼″ (6 mm) | Cabinet backs, underlayment | Not structural |
| ⅜″ (10 mm) | Wall sheathing, paneling | Sometimes wall in non-bracing zones |
| ½″ (12 mm) | Wall sheathing, roof sheathing | Most common exterior |
| ⅝″ (16 mm) | Roof sheathing (heavier loads), thicker walls | Snow zones, T&G option |
| ¾″ (19 mm) | Subfloor, stair treads | Tongue-and-groove for subfloor |
| 1⅛″ (29 mm) | Heavy subfloor, mezzanines | Specialty |
Plywood vs OSB vs MDF — when to use which
- CDX plywood: exterior glue, exposure-rated, for any structural exterior application (sheathing, subfloor). Stronger than OSB ply-for-ply in cyclical wet/dry conditions.
- OSB (Oriented Strand Board): structural rated equivalents of CDX, typically 10 – 20 % cheaper. Slightly heavier; edges swell more when wet. Industry standard for wall and roof sheathing today.
- MDF (Medium Density Fiberboard): for interior, non-structural use — paint-grade cabinet doors, base molding, mantle pieces. Smooth surface, machines cleanly. Not water-resistant.
- BCX / sanded plywood: for visible interior applications and shelving — one sanded face for paint, the other utility.
Frequently asked questions
How many sheets of plywood for a 12×12 room?
12 × 12 = 144 ft². With 10 % waste = 158 ft². At 32 ft² per 4×8 sheet: ⌈158 ÷ 32⌉ = 5 sheets. For subfloor, add 1 extra sheet for sacrificial cuts around plumbing penetrations.
How many sheets of plywood for a 1,000 sq ft house subfloor?
1,000 × 1.10 = 1,100 ft². At 32 ft² per 4×8: ⌈1,100 ÷ 32⌉ = 35 sheets. For larger jobs, switching to 4×10 (40 ft²) or 4×12 (48 ft²) sheets reduces seams and labour, though stock and handling become harder.
Should I use plywood or OSB for sheathing?
OSB is the industry standard for wall and roof sheathing in 2026 — it is roughly 10-20 % cheaper than CDX plywood with comparable structural performance. CDX is preferred when there is a high risk of intermittent wetting during construction (delayed roofing, monsoon climates).
How many sheets of plywood for a 20×30 floor?
600 ft². With 10 % waste = 660 ft². At 32 ft² per 4×8 sheet: ⌈660 ÷ 32⌉ = 21 sheets. Switching to 4×8 ¾″ T&G subfloor at $35-40 each (2026), that is around $735-840 of subfloor.
What is the actual size of a 4×8 sheet of plywood?
Plywood is one of the few materials where nominal = actual. A 4×8 sheet measures exactly 48″ × 96″. The thickness, however, is usually slightly less than nominal — a "¾″" sheet measures 23/32″ (about 18.2 mm).
How much waste should I add for plywood?
For straight rectangular layouts (subfloor, wall sheathing): 10 %. For roof sheathing with hips and valleys: 12-15 %. For curved or angled layouts (decorative panels, herringbone): 15-20 %.
How heavy is a 4×8 sheet of plywood?
A ¾″ CDX 4×8 sheet weighs about 65 lb (29 kg). ½″ is about 45 lb (20 kg). For OSB equivalents, expect 5-10 % heavier per equivalent thickness.