Plywood Sheathing Calculator
Calculate plywood or OSB sheathing sheets for roofs, walls, or subfloors. Choose sheathing type, roof pitch, and get weight and cost estimates.
🪵 Plywood Sheathing Calculator
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💡 Plywood Sheathing Estimation
Plywood and OSB sheathing form the structural substrate of US residential roofs, walls, and subfloors. Accurate sheet estimation prevents costly jobsite delays and excess material waste. The calculator above accounts for roof pitch multipliers — the often-overlooked factor that increases actual roof area compared to the flat footprint.
Choose from 6 sheathing types, select your application (roof, wall, subfloor), pick the roof pitch, and get sheets, weight, and cost instantly.
Estimate roofing with our roofing calculator. For general plywood, use our plywood calculator. Find your pitch with our roof pitch calculator.
Sheathing Types
| Type | Thickness | Weight (4×8) | Cost (4×8) | Best For |
|---|---|---|---|---|
| CDX Plywood ½" | 15/32" actual | ~42 lbs | $28–$35 | Roof sheathing (16" OC rafters) |
| CDX Plywood ⅝" | 19/32" actual | ~51 lbs | $35–$42 | Roof sheathing (24" OC rafters) |
| CDX Plywood ¾" | 23/32" actual | ~60 lbs | $40–$50 | Heavy roofs, snow loads, solar panels |
| OSB 7/16" | 7/16" actual | ~38 lbs | $18–$25 | Wall sheathing, light-duty |
| OSB ½" | 15/32" actual | ~44 lbs | $22–$30 | Roof and wall sheathing |
| T&G Plywood ¾" | 23/32" actual | ~62 lbs | $42–$55 | Subfloor (tongue-and-groove) |
Roof Pitch Multiplier Table
A pitched roof has more surface area than its flat footprint. Multiply the footprint area by the pitch multiplier to get the actual roof area.
| Roof Pitch | Multiplier | 600 sq ft Footprint | Sheets (4×8) |
|---|---|---|---|
| Flat (0/12) | 1.000 | 600 sq ft | 19 |
| 2/12 | 1.014 | 608 sq ft | 19 |
| 4/12 | 1.054 | 632 sq ft | 20 |
| 6/12 | 1.118 | 671 sq ft | 21 |
| 8/12 | 1.202 | 721 sq ft | 23 |
| 10/12 | 1.302 | 781 sq ft | 25 |
| 12/12 (45°) | 1.414 | 849 sq ft | 27 |
Note: A steeper pitch dramatically increases sheathing needs. A 12/12 pitch requires 41% more sheets than a flat roof over the same footprint.
Step-by-Step Sheathing Estimation
Step 1: Measure the Area
For roofs: measure the building footprint (length × width). For a gable roof, this is the total footprint of both sides. For walls: measure perimeter × wall height. For subfloors: measure room length × width.
Step 2: Apply Pitch Multiplier (Roofs Only)
Multiply footprint by the pitch multiplier from the table above. Formula: Multiplier = √(1 + (pitch/12)²).
Example: 30 ft × 20 ft = 600 sq ft × 1.054 (4/12) = 632 sq ft actual roof area.
Step 3: Calculate Sheets
Divide actual area by 32 sq ft (one 4×8 sheet). Add 10% waste for simple roofs, 15% for complex roofs with hips, valleys, and dormers.
Example: 632 sq ft × 1.10 = 695 sq ft ÷ 32 = 21.7 → 22 sheets.
Plywood vs. OSB for Sheathing
| Feature | CDX Plywood | OSB |
|---|---|---|
| Cost | $28–$50/sheet | $18–$30/sheet |
| Moisture | Better — dries quickly | Swells at edges when wet |
| Nail holding | Better at edges | Good in field, weaker at edges |
| Uniformity | May have voids | Very uniform (no voids) |
| Weight | Slightly lighter | Slightly heavier (same thickness) |
| Code approval | Yes | Yes |
Recommendation: Both are code-approved for structural sheathing. Use CDX plywood in moisture-prone areas (bathrooms, kitchens, coastal climates). Use OSB to save 20–30% on material cost where moisture isn't a concern.
Sheathing by Application
| Application | Recommended | Min Thickness | Spacing |
|---|---|---|---|
| Roof (16" OC) | CDX ½" or OSB ½" | 7/16" | ⅛" gap between sheets |
| Roof (24" OC) | CDX ⅝" or OSB ⅝" | ½" | ⅛" gap between sheets |
| Wall | OSB 7/16" or CDX ½" | 7/16" | ⅛" gap, stagger joints |
| Subfloor (16" OC) | CDX ¾" or T&G ¾" | ⅝" | T&G eliminates gaps |
| Subfloor (24" OC) | T&G ¾" or CDX ¾" | ¾" | Glue + screw recommended |