Free Tool
Free insulation calculator
Enter your area and target R-value and get the batts or blown-in bags you need, with coverage and a waste allowance built in. Free, no signup.
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Buy the right amount for the R-value
Insulation is sold two ways, and this calculator handles both. Batts and rolls come in bundles rated for a set R-value and a set coverage. Blown-in comes in bags, and how far a bag goes depends on how deep you blow it to hit the R-value.
Pick your target R-value first. Attics usually want R-38 to R-49, a 2x6 wall runs R-19 to R-21, and a 2x4 wall takes R-13 to R-15. Your local energy code sets the minimum, so check it before you buy.
Then enter the area. For batts the calculator returns the number of bundles from the coverage rating. For blown-in it returns bags from the coverage needed to reach your R-value. Both get your waste allowance and round up.
The coverage on the package is the number that counts, and it moves a little by brand, so always confirm against the label before you check out.
Insulation Calculator questions
How much insulation do I need?
Enter the area and the R-value you are targeting. The calculator returns the bundles of batts or the bags of blown-in, with waste added and the counts rounded up.
What R-value should I use?
Attics commonly run R-38 to R-49, 2x6 walls R-19 to R-21, and 2x4 walls R-13 to R-15. Your local energy code sets the required minimum for your area.
Batts or blown-in?
Batts are simple for open walls and floors. Blown-in fills an attic fast and gets into gaps. The calculator estimates either one, so you can compare.
Is this really free?
Yes. No email, no signup, and nothing you type leaves your browser.
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Disclaimer: These free tools and templates are provided for general information and estimating purposes only. All results — including quantities, material and cost estimates, load, sizing, and span figures, scores, and any guidance or warnings — are rough approximations that may not fit your specific project, site conditions, local building codes, or current prices. They are not engineering, architectural, structural, legal, financial, or other professional advice, and are not a substitute for a licensed engineer, architect, contractor, or other qualified professional. Always confirm quantities, sizing, and structural, electrical, mechanical, and code requirements with a licensed professional and your local authority having jurisdiction before purchasing materials or performing any work. Werx makes no warranty as to accuracy and accepts no liability for any decision made using these tools. Use at your own risk. See our Terms of Service.