Insulation Calculator
Enter the area to insulate and the coverage printed on the bag to see how many bags or rolls to buy.
How much insulation do I need?
Measure the area (length x width for attics, length x height for walls), add about 5% for cuts, and divide by the square feet each bag covers. Coverage depends on the product and R-value, so always use the number printed on the bag.
Typical targets in the US: R-13 to R-15 for 2x4 walls, R-19 to R-21 for 2x6 walls, R-30 for floors, and R-38 to R-60 for attics depending on climate. Check your local energy code.
Questions
What R-value do I need in my attic?
Most of the US calls for R-38 to R-60 in attics. Colder climates need the higher end.
Can I use the same calculator for blown-in insulation?
Yes, if you enter the coverage per bag for the depth you want. Blown-in bags list coverage for each R-value on the label.
Do I subtract windows and doors?
For walls, yes: subtract the area of large windows and doors. For attics, use the full floor area.