Attic Insulation Calculator
Blown-in attic insulation is sold in bags, and each bag covers a set area at a set depth. This shows how many bags a floor needs at the depth you plan to add.
- Free
- Works offline after your first visit
- Saves on this device
- No sign-up
- Updated
How it works
Divide the floor area by the area one bag covers at your depth, then round up to a whole bag. The volume is the floor area times the depth, shown for reference.
Coverage depends on the product and the depth, so use the figure on your own bag label rather than the number that opens here.
Worked example
An attic floor of 1,000 ft², with 10 in of new insulation added, needs about 833.3 ft³ of material. At the coverage you entered, that is 25 bags bags.
Questions
Why round up to whole bags?
A bag cannot be split. Rounding up means you will not run short partway across the floor.
Should I measure the whole roof?
Measure the floor you will cover, the flat area over the joists. Sloped roof area is a different number.
How deep should I add?
Check the depth your local building guidance or energy program asks for, then match the depth printed on the bag label.
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