Blown-In Insulation Calculator

The US Department of Energy recommends R-38 to R-49 for warmer climate zones 1 to 3, and R-49 to R-60 for colder zones 6 to 8. Look up your own zone before setting a target, because the gap between those two ranges is several inches of material and real money.

Yes. Subtract what is already up there from your target, so the calculator sizes only the material you are adding. Going from R-10 to R-49 means adding R-39, not R-49, and getting that wrong is an expensive way to over-order.

Because yield comes from density and settled R-value per inch, and both differ by brand and by material. A generic figure can be off by enough to leave you short halfway across an attic. The coverage chart is printed on the bag, so bag yield is a field you fill in here instead of a number we picked for you.

No. Spray foam goes on as a liquid and expands, so it is estimated by kit yield in board feet at a target thickness, which is a different calculation entirely. This one handles blown-in cellulose and loose-fill fiberglass.