Insulation Calculator
An insulation calculator works out how much insulation you need from the area you are covering and the target R-value. For batts, it divides the area by the coverage per bag or roll. For blown-in, it uses the bag coverage at your target R-value. Enter your area and R-value below to get the bags or batts needed.
Enter the area and the bag's coverage at your target R-value.
How Do You Calculate How Much Insulation You Need?
To calculate insulation, measure the area to cover (wall or attic square footage), then divide by the coverage of one bag or roll at your target R-value. Batt rolls list their square foot coverage, and blown-in bags list coverage at each R-value on the bag. A 1,000 square foot attic at R-38 might need a certain number of bags listed on the product. The calculator divides your area by the coverage you enter.
What R-Value Do You Need?
R-value measures resistance to heat flow, and the right level depends on the location and climate: attics often target R-38 to R-60, walls R-13 to R-21, and floors R-25 to R-30, with colder climates needing more. Higher R-value means more material (thicker batts or more blown-in bags). The calculator works from the coverage your product lists at the R-value you choose, so set the target for your climate zone.
Batts or Blown-In Insulation?
Batts are pre-cut rolls fitted between studs and joists, simple for walls and open framing. Blown-in (loose-fill) insulation is blown into attics and cavities, filling gaps better and good for irregular spaces. The estimating differs: batts by area and roll coverage, blown-in by bags at a target R-value. The calculator handles both: enter the coverage figure from whichever product you choose.
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Frequently asked questions
- How much insulation do I need?
- Divide the area to cover by the coverage of one bag or roll at your target R-value, which the product lists. The calculator does this from your area and coverage.
- What R-value do I need for my attic?
- Attics often target R-38 to R-60 depending on climate, with colder zones needing more. Walls are usually R-13 to R-21.
- Should I use batts or blown-in insulation?
- Batts suit walls and open framing; blown-in fills attics and irregular cavities better. The calculator estimates either from your area and product coverage.