Blown-In Insulation Bags Calculator

1. 1Enter attic area (sq ft).
2. 2Enter target r-value.
3. 3Read your bags needed on the right — it updates as you type.
4. 4Hit Share to keep the scenario or send it to someone.

About this calculator

Blown-in insulation — whether cellulose or fiberglass — is sold in bags with a printed coverage chart showing how many square feet one bag covers at various depths and R-values, since blown-in material's insulating power depends on how thick a layer it's blown to. This calculator uses a simplified version of that chart: you enter your attic's square footage and your target R-value, and it estimates bags needed based on typical cellulose coverage rates (roughly 30-40 sq ft per bag at R-38, less at higher R-values like R-49 or R-60 since a deeper, denser layer is needed). Because manufacturers vary in exact bag coverage and settle differently over time, this is a solid planning estimate, but always cross-check against the specific bag's printed chart at the store, which lists exact square-foot coverage per bag for each target R-value and installed depth. Adding blown-in insulation over existing attic insulation to boost R-value is one of the most cost-effective energy upgrades a homeowner can make, and getting the bag count close before rental of a blower machine (often required with bulk bag purchases) avoids a second supply run mid-job.

What each field means

FAQ

Accuracy and limitations

• Estimates assume standard, average conditions — local rules, pricing, and materials vary.
• Results are rounded for readability; add a buffer before ordering, booking, or committing.
• Double-check anything with a real cost attached against a local quote.