Insulation Calculator
Calculate how many rolls, batts, or bags of insulation you need for an attic, wall, or floor area.
How to measure for insulation
Measure the length and width of the area you're insulating — an attic floor, wall cavity, or crawl space. Then find the coverage figure printed on your chosen insulation product for the depth/R-value you need, and enter it here.
Required R-value depends on your climate zone and local building code — check that first, then find a product/depth that meets it before using this calculator to work out quantity.
Frequently asked questions
How much insulation do I need?
Measure the area you're insulating (attic floor, wall cavity, etc.), add a waste allowance for cuts and trimming, then divide by how much area one package covers at your chosen depth/R-value.
Where do I find the coverage per package?
It's printed on the product packaging — insulation rolls, batts, and bags are labeled with the area they cover (e.g. "covers 88.8 sq ft") for a given thickness and R-value. Use that figure here.
Does this calculator tell me what R-value I need?
No — required R-value depends on your climate zone and local building code. Check your local energy code or a professional before buying, then find a product/depth combination that meets it and use its stated coverage here.
What waste allowance should I use for insulation?
10% is reasonable for a simple rectangular area. Increase it for spaces with lots of obstructions (joists, wiring, plumbing) that require more cutting and fitting.
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