Blown In Insulation Calculator
Calculate the amount of blown-in insulation needed for your attic or walls. Input area dimensions and desired R-value to estimate bags required and cost.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Blown-In Insulation Calculator
This calculator estimates the number of insulation bags and total cost for a rectangular attic or floor area. All measurements are in feet and US dollars.
- Enter Length & Width (in feet) of the area you want to insulate.
- Select Desired R-Value (e.g., R-30, R-38). This determines insulation thickness.
- Choose Bag Coverage that matches your insulation material (fiberglass or cellulose) and the R-value you selected. Each option shows the square footage one bag covers at that R-value.
- Enter Cost per Bag in dollars (e.g., 15.00).
- Click Calculate. The results show:
- Area (sq ft) = length × width
- Bags Needed = rounded up (ceil) of area ÷ coverage per bag
- Total Cost = bags × cost per bag
Tip: Ensure your bag coverage option matches the R-value you selected for accurate results.
Previous Results
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Frequently Asked Questions
The calculator divides the total area (length × width) by the coverage per bag for the selected R-value, then rounds up to the nearest whole bag.
Recommended R-values vary by climate zone. For attics, R-30 to R-60 are common. Check local building codes for your area.
No, it assumes a flat open area. For irregular spaces, consider adding 10-15% extra material.