Blown-In Insulation Calculator
Estimate whole bags from the coverage chart for the exact loose-fill product and target R-value you plan to install.
Compare two product options using your calculated requirement
Only compare manufacturer chart rows that describe the same target R-value, installed depth and required installation conditions. Enter both products' allowable square-foot coverage per bag and actual bag prices. The result compares whole-bag material cost, not equipment rental, installation or compliance.
Area to cover at the selected insulation specification: Run or update the calculator above.
This comparison uses only the coverage/yield and price values you enter. It does not rank brands, fetch retailer data, include tax or delivery, or replace product specifications.
How bag count is calculated
The calculator first resolves the attic, wall or other project area. When you enter the maximum coverage per bag from the manufacturer chart, it divides area by that product-specific coverage and rounds upward to a whole bag.
bags = ceiling(area ÷ coverage per bag)
The optional R-value and installed-depth fields are references only. They do not change the math by themselves because the coverage value must already correspond to those installation conditions.
Why bag coverage cannot be universal
Loose-fill yield changes with material, installed depth, density and target thermal resistance. Two products can require different bag counts for the same attic area and R-value. For that reason, ProjectCalcWorks does not hide a generic bags-per-square-foot assumption inside the result.
Use the exact coverage table printed on the bag or current manufacturer documentation. If the chart gives several rows for different R-values, select the row that matches your project requirement before entering the square-foot coverage here.
R-value is a project requirement, not a calculator default
Recommended or required insulation levels vary by climate, building component, existing assembly and applicable code. ENERGY STAR provides climate-oriented insulation guidance, but a project-specific requirement can differ. This calculator therefore records your target R-value without choosing it for you.
Blown-in versus batts, rolls and boards
This tool is for loose-fill products whose packaging provides a coverage chart. For insulation sold as batts, rolls or rigid boards with a fixed square-foot package coverage, use the Insulation Calculator instead.
Related calculators
Insulation Calculator · Drywall Calculator · Stud Wall Calculator
Example: a higher-yield bag is not necessarily cheaper to buy
For a hypothetical 1,200 sq ft attic at a separately verified target R-value, suppose the relevant product-chart row for Product A permits 45 sq ft per bag and the supplier quotes $23 per bag. Ceiling(1,200 ÷ 45) = 27 bags, or $621 in material. Product B's equivalent chart row permits 32 sq ft per bag and is priced at $16 per bag: ceiling(1,200 ÷ 32) = 38 bags, or $608. Product B is $13 cheaper on these illustrative material prices despite needing more bags.
Before comparing real quotes, verify that the coverage figures are permitted for the same target R-value, installed thickness and minimum-bag-count requirement. Do not select a chart row simply because it has higher stated coverage, and account separately for equipment, installation labor, access and other actual charges. Enter the verified chart values into the comparison above rather than relying on these invented examples.
Compare two manufacturer-chart coverages
Suppose an attic has 1,200 sq ft of net area, and you have already selected the insulation type and required installed R-value. If the exact manufacturer's chart for that combination permits 45 sq ft of coverage per bag, ceiling(1,200 ÷ 45) requires 27 bags. A different hypothetical product or coverage row allowing 32 sq ft per bag needs ceiling(1,200 ÷ 32) = 38 bags. Neither rate is a recommendation; the exercise demonstrates why bag counts cannot be compared without checking the chart row.
For a real project, ensure the chosen row uses the same target R-value, installed thickness and minimum bag count conditions as your design. Do not substitute a manufacturer's maximum-coverage row for a higher R-value installation. See the source register for the manufacturer coverage-chart policy.