Roof Sheathing Calculator

By Calculator Academy / December 11, 2025

Roof Sheathing Calculator

Calculate exactly how many OSB or plywood sheets you need for your roofing project.

Roof Type *

Gable Two sloped sides Hip Four sloped sides Shed Single slope Flat No slope

Building Dimensions *

Length (feet)

Width (feet)

Overhang (inches)

Roof Pitch *

Angle: 18.4°

4/12

Select your roof's pitch (rise per 12 inches of run)

Sheathing Material *

OSB Oriented Strand Board Cost-effective Plywood CDX or Structural Premium durability

Sheet Thickness

7/16" 11mm 15/32" 12mm 1/2" 12.7mm 5/8" 15.9mm 3/4" 19mm

Light residential use

Standard Sheet Size: 4 × 8 ft (32 sq ft/sheet)

Waste Factor 10%

0% 30%

Price per Sheet ($)

Optional: Enter local pricing for cost estimation

Calculation Results

Sheets Needed — OSB sheets (7/16" thick)

Roof Area — sq ft

With Waste — (+10%)

Pitch Details — Multiplier: —

Order Summary

Roof Type: Gable

Material: OSB 7/16"

Sheet Size: 4' × 8'

Total Sheets: — sheets

OSB vs Plywood Comparison

Compare the two most popular roof sheathing materials

Feature	OSB	Plywood
Cost	✓ Lower	Higher
Moisture Resistance	Moderate	✓ Better
Weight	Heavier	✓ Lighter
Nail Holding	Good	✓ Excellent
Edge Swelling	More prone	✓ Less prone
Availability	Widely available	Widely available
Span Rating	Equivalent	Equivalent
Eco-Friendly	✓ Uses smaller trees	Larger trees needed

Recommendation: OSB is ideal for budget-conscious projects with good ventilation. Plywood is better for humid climates or when premium durability is needed.

How to Use This Calculator

Select Roof Type

Choose between gable, hip, shed, or flat roof styles.

Enter Dimensions

Input your building's length, width, and roof overhang.

Set Pitch & Material

Select your roof pitch and preferred sheathing material.

Get Results

View sheets needed, total area, and estimated cost instantly.

Calculation Formula

Pitch Multiplier = √(rise² + 12²) ÷ 12

Roof Area = (Length × Width) × Pitch Multiplier

Total Area = Roof Area × (1 + Waste Factor)

Sheets Needed = ⌈Total Area ÷ Sheet Area⌉

Standard sheets are 4' × 8' (32 sq ft) in imperial or 1.22m × 2.44m (~2.98 sq m) in metric. The calculator rounds up to ensure you have enough material.