Blown-In Insulation Calculator
Bags of blown-in attic insulation needed.
Enter your values
ⓘ Live results
Results
- Bags needed
- 47
- Required blown depth
- 18.1 in
- Coverage per bag at this depth
- 26 sq ft
Quick answer
Bag count comes from the attic area, the target R-value and the bag's coverage chart rate per inch of depth.
bags = ceil(area x depth / coverage per bag at that depth)
How to use the Blown-In Insulation Calculator
- 1Enter the attic area and your target R-value for your climate zone.
- 2Use the R-value per inch from the bag's coverage chart.
- 3The calculator adjusts bag coverage for the actual depth you need.
Worked example
Using the values the calculator loads with:
Inputs
- Attic area1200 sq ft
- Target R-value49
- R-value per inch2.7
- Bag coverage35 sq ft per bag at 13.5 in
Results
- Bags needed47
- Required blown depth18.1 in
- Coverage per bag at this depth26 sq ft
Frequently asked questions
What R-value does my attic need?
Cold climates often target R-49 to R-60, milder climates R-30 to R-38 — check local energy code.
Fiberglass or cellulose?
Cellulose is denser and settles more, so check the bag chart depth for your specific product.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.