How to use this calculator
- Add each rectangular wall, ceiling, or project area.
- Enter the combined area of openings not receiving insulation.
- Choose waste and enter coverage per package, batt bundle, or roll.
- Calculate adjusted area and whole packages.
How the calculation works
Measured areas are combined, openings are deducted, waste is applied to the net area, and the result is divided by the coverage value you enter before rounding up.
Formula
Net insulation area = gross area − openings Adjusted area = net area × (1 + waste %) Packages = ceil(adjusted area ÷ entered package coverage)
Worked example
Two areas totaling 500 sq ft less 20 sq ft of openings leave 480 sq ft. With 5% waste, plan for 504 sq ft. At an entered 40 sq ft per package, that rounds to 13 packages.
Project considerations
- Package coverage is product-specific and must be entered from the selected product.
- This tool does not recommend insulation type, R-value, vapor control, or climate-zone requirements.
- Irregular cavities and installation conditions may require project-specific adjustment.
Frequently asked questions
Does this choose an R-value?
No. It only estimates coverage quantity from the measurements and package coverage entered.
Can rolls and batts be calculated?
Yes, when the selected package, bundle, or roll has a known coverage area.