Enter the area to insulate and your product’s per-package coverage to see how many packages to buy, waste included.
How insulation is bought
Every batt and roll package prints its coverage in square feet — and that number changes with R-value, width and thickness, which is why this calculator asks for it instead of guessing. Enter the area, the coverage from the label of the product you’ve chosen, and a cutting allowance, and it returns whole packages.
How to use it
- Measure the area: wall height × length for walls, floor area for attics — openings usually stay in as waste.
- Read the coverage per package off the product label or listing.
- Keep 10% waste for standard framing; more for irregular bays.
The formula
A worked example
1,000 sq ft of attic with 10% waste needs 1,100 sq ft of product — at 40 sq ft per package that is 28 packages. The R-value decision comes first, though: attics in cold climates commonly target R-49–R-60, walls far less — and higher R means thicker product, smaller per-package coverage, and more packages for the same area.