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Insulation Calculator
Find how many bags of insulation you need.
Bags needed
—
Rounded up.
| Area | — |
|---|---|
| Coverage/bag | — |
| Exact bags | — |
| — |
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Enter your figures above to see the step-by-step working.
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How the Insulation Calculator Works
Blown-in and batt insulation is sold by the bag or roll, each covering a set number of square feet at a target R-value. Divide the area you’re insulating by the coverage printed on the bag, then round up. Covering 1,000 square feet of attic at 40 square feet per bag takes 25 bags.
Coverage drops as the target R-value rises, so check the bag’s coverage chart for the R-value you want — higher R-values mean fewer square feet per bag.
bags = area ÷ coverage per bag (rounded up)
Frequently Asked Questions
How many bags of insulation do I need?
Divide the area by the coverage per bag from the label, then round up. 1,000 ft² at 40 ft²/bag is 25 bags.
Why does coverage change?
Higher R-values need more material, so each bag covers fewer square feet. Use the coverage for your target R-value.
What R-value do I need for an attic?
Commonly R-38 to R-60 depending on climate — check local code and the bag chart.
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