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Blown-In Insulation Bag Count Calculator

Calculate how many bags of blown-in insulation are needed for an attic or wall cavity at a target depth.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax

Bags needed

12 bags

Check your inputs

Bag yield depends on the target installed density, which varies by depth and product per the manufacturer's coverage chart — always use the yield figure printed on the bag for your specific target depth/R-value, not a generic assumption.

Total insulation volume
39.24 yd³

With the figures above, the bags needed comes to 12. The method behind this is well established, though site conditions and material batches will move it somewhat. This is calculated for United States and cites IRC 2024. Building in another market? Change the selector above so the units and code reference follow.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Bags needed = ceil(required volume ÷ the bag's rated coverage yield at the installed density), the standard method for estimating blown-in (loose-fill) insulation material from the manufacturer's bag coverage chart

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Frequently asked questions

Why does bag coverage yield change with depth?
Manufacturers publish coverage charts because a bag contains a fixed mass of material — installing it at a greater depth (higher density, for higher R-value per inch) compresses that same mass into less floor area, so the coverage yield per bag drops as target depth increases.
Should I round up the number of bags?
Yes — bags are a whole-unit product, so the required volume is divided by the per-bag yield and rounded up to ensure full coverage at the target depth across the whole area.
Does settling reduce the depth over time?
Loose-fill insulation can settle somewhat after installation, which is why manufacturers' coverage charts already build in an initial installed depth that accounts for expected settling to reach the rated long-term R-value — always install to the chart's stated initial depth, not just the nominal settled depth.