Insulation Calculator
Calculate insulation materials needed for attics, walls, floors, and basements. Supports fiberglass batts, blown-in fiberglass, blown-in cellulose, spray foam, and rigid foam board with R-value recommendations by climate zone.
~21 sq ft each (3x7 ft)
~15 sq ft each (3x5 ft)
Insulation Estimate
Gross Area
1,200
sq ft
Net Area (minus openings)
1,200
sq ft
Adjusted Area (with waste)
1,320
sq ft
Coverage Per Package
42.67
sq ft / pkg
Packages to Buy
31
bags (4 batts)
Installed Thickness
12"
R-38
Climate Zone Recommendations
Select R-values based on your climate zone per IRC 2021. Higher climate zone numbers indicate colder climates requiring more insulation.
Zone 1-3 (Hot / Mixed)
Attic: R-30 to R-49
Zone 4-5 (Mixed / Cool)
Attic: R-38 to R-60
Zone 6-7 (Cold / Very Cold)
Attic: R-49 to R-60
R-Value Reference Table (IRC 2021)
| Climate Zone | Attic | Exterior Walls | Floor | Basement Walls |
|---|---|---|---|---|
| Zone 1-3 | R-30 to R-49 | R-13 to R-15 | R-13 | R-13 |
| Zone 4-5 | R-38 to R-60 | R-15 to R-21 | R-19 to R-25 | R-15 to R-21 |
| Zone 6-7 | R-49 to R-60 | R-19 to R-21 | R-25 to R-30 | R-19 to R-21 |
How to Use This Calculator
Select the application (attic, walls, floor, or basement), enter the area dimensions or square footage directly, choose your target R-value and insulation type, and subtract any door or window openings. The calculator shows the number of packages, bags, sheets, or kits needed including waste factor. Refer to the climate zone table below to pick the right R-value for your region.
Formula Used
Net Area = Gross Area - Door Openings - Window Openings. Packages = (Net Area x (1 + Waste%)) / Coverage Per Package.
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Disclaimer
This calculator is for estimation purposes only. Results may vary based on local conditions, materials, and building codes. Always consult a licensed professional before making decisions based on these calculations. MyContractorTools is not responsible for any errors or omissions.