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Insulation Calculator

Estimate insulation area, packages, and batts or rolls based on wall or attic coverage.

Insulation Calculator
✓ Your estimate
Estimated insulation needed
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packages
Switch display unit only.
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Net sq ft
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Sq ft incl. waste
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Packages
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Batts/roll pieces
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What this estimate includes

This estimate shows insulation coverage area, package count, and batt or roll-piece count based on the product coverage you enter.

How it’s calculated

Net area = length × height − openings
Adjusted area = net area × waste %
Packages = adjusted area ÷ package coverage, rounded up
Batts/roll pieces = adjusted area ÷ piece coverage, rounded up

Before you order

Insulation coverage depends on R-value, product type, framing spacing, and compression. Confirm package coverage on the product label before buying.

Frequently Asked Questions

What package coverage should I enter?
Use the coverage listed on the insulation package for the exact R-value and product type.
Should I subtract windows and doors?
Yes, subtract large openings for wall insulation to avoid overbuying.
Does this choose the right R-value?
No. It estimates quantity only. Choose R-value based on your local code and project area.
What is the difference between batt and blown-in insulation?
Batts are pre-cut panels designed to fit between studs or joists. Blown-in insulation is loose fill blown into cavities using a machine — common for attics and retrofit walls where batts cannot be installed without opening the wall.
How do I calculate insulation for multiple walls?
Add the area of all walls together (length times height for each), then subtract the total area of windows and door openings. Enter the resulting net square footage into the calculator.
What R-value do I need?
R-value requirements depend on your climate zone and where you are insulating. Attics typically need R-38 to R-60, walls R-13 to R-21, and floors R-25 to R-30. Check your local building code or the DOE insulation recommendations for your zip code.
Can I add insulation on top of existing insulation?
Yes, for attics you can add new insulation directly on top of existing insulation to reach a higher R-value. Do not compress existing insulation — compression reduces its R-value. For walls, adding on top is only practical if you are re-drywalling.
Disclaimer: This calculator provides estimates only. Actual quantities depend on product coverage, jobsite conditions, waste, and supplier details. Verify all quantities before ordering. See all interior material calculators.