Estimate blown-in insulation bag count from attic area, product coverage per bag at the chosen R-value and waste. Plan cellulose or fiberglass quantity.
Enter your measurements and material details.
Use the coverage-per-bag value from the manufacturer chart for the exact target R-value or installed depth, not a generic bag average.
Blown-in insulation manufacturers publish bag-count or coverage charts for different target R-values and installed depths. This calculator uses that product-specific coverage figure rather than trying to infer density from a generic formula.
Measure the attic floor or ceiling area being insulated. Determine the target insulation level from the project requirements, then find the corresponding square-foot coverage per bag on the product chart. Enter that value directly.
Divide adjusted attic area by the manufacturer coverage per bag for the target R-value.
Higher R-values generally require more installed material per square foot.
Yes if you use the product-specific coverage chart.
A modest allowance can cover inaccessible areas and installation variation.
No. It calculates quantity after you select a target based on the project requirements.
Using the example inputs shown in the calculator — Attic/ceiling area (sq ft) = 1200, Coverage per bag at target R-value (sq ft) = 40, Extra allowance (%) = 8 — the result is 33 bags. This demonstrates the formula with a complete set of numbers rather than a hidden assumption.
The result breakdown also shows Adjusted area: 1,296 sq ft; Coverage per bag: 40 sq ft. Replace the example values with field measurements and the exact product coverage, yield or package size you plan to buy.
For this blown-in insulation calculator, the inputs with the greatest practical effect are attic/ceiling area, coverage per bag at target r-value and extra allowance. Recalculate when any of those change; do not reuse a result from a different room, run, layer depth or product specification.
A useful blown-in insulation estimate begins with dimensions taken from the actual project. Small measurement errors can become significant when they are repeated across many boards, joints, courses, bags or rolls. Record the dimensions you used and keep net geometry separate from the purchase allowance so the result can be checked later.
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