Attic Insulation Calculator

Estimate how many bags of blown insulation an attic needs.

BAGS NEEDED
— bags
blown insulation

Usage Tip

Air seal first. Blown insulation laid on top of air leaks just wastes money.

THE MATH
bags = Area × R ÷ (coverage × 38)
Where: coverage = sq ft per bag at R-38  •  R = target R-value
• Coverage scales with the target R-value
• Air-seal before adding insulation
Scroll to Top

The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.