Blow In Insulation Calculator
Estimate the number of bags of blow-in insulation needed for your attic or walls based on area and desired R-value.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Blow-In Insulation Calculator
This tool calculates the number of insulation bags needed for your attic or wall cavity. All inputs are in imperial units (square feet).
- Enter Area – Type the total square footage of the space to insulate (e.g., 1000).
- Select Desired R-Value – Choose from common attic values (R-30 to R-60). R-38 is a typical default.
- Adjust Bag Coverage – The default (40.4 sq ft @ R-38) matches standard fiberglass. Change it if your product has different coverage.
- Click "Calculate" – The result shows the total bags needed (rounded up to the nearest whole bag).
Tip: If you see a red error, ensure both number fields are positive. The result includes a breakdown of your inputs and the rounded bag count.
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Frequently Asked Questions
Blow-in insulation is loose-fill material (fiberglass, cellulose, or mineral wool) that is blown into attics or wall cavities to improve thermal resistance.
Recommended R-values vary by climate zone. Consult local building codes or the U.S. Department of Energy's map for your area.
This calculator provides an estimate. Actual coverage depends on installation technique and product specifications. Always buy a little extra to account for waste.