Insulation Calculator
Estimate insulation materials for your walls, attic, or ceiling. This calculator supports fiberglass batts, blown-in cellulose, and spray foam — with the correct R-value for each application based on common building standards.
Enter Your Details
Full Breakdown
Area
Insulation Type
Application
R-Value
Thickness
Stud Spacing
Quantity Needed
Coverage per Unit
How to Use This Calculator
- Choose your input method — enter dimensions or total square footage.
- Select the insulation type: fiberglass batt, blown-in cellulose, or spray foam.
- Choose the application — walls (R-13), attic (R-30), or cathedral ceiling (R-38).
- Set your stud spacing (16" OC is most common).
- Click "Calculate Insulation" for quantities and coverage details.
The Formula
Units Needed = Total Area ÷ Coverage per Unit
Common R-values by application:
- R-13: Standard exterior walls (2×4 framing)
- R-30: Attic floors
- R-38: Cathedral ceilings and some attics in cold climates
Coverage per unit varies by insulation type:
- Batt: ~88 sq ft per bundle (R-13, 16" OC)
- Blown-in: ~40 sq ft per bag (R-13), ~18 sq ft per bag (R-30)
- Spray foam: ~200 board feet per kit