Home Improvement

Insulation Calculator

Calculate how much insulation you need.

Enter your wall or attic area to calculate how many packages of batt or roll insulation to buy.

Enter a valid area.

Insulation Packages Needed

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How to Use This Tool

  1. Measure the total area in square feet.
  2. Adjust the coverage per package (sq ft) if your product differs from the default.
  3. Click Calculate to see how much you need, including a waste allowance.

The Coverage Formula

packages Needed = (Area × (1 + Waste %)) ÷ Coverage per Unit

This calculator adds your specified waste allowance to the raw area before dividing by coverage, ensuring you order enough to account for cuts, mistakes, and pattern matching.

Why Waste Allowance Matters

A 10% waste allowance is a common industry default, but complex layouts, diagonal patterns, or a room with many corners and cutouts may need a higher allowance (15-20%), while simple rectangular rooms may need less.

Frequently Asked Questions

How much waste allowance should I use?

10% is a common default for straightforward rectangular areas. Increase to 15-20% for complex layouts, diagonal installations, or rooms with many corners, alcoves, or obstacles.

What if my product's coverage rate is different?

Adjust the "Coverage per Package (sq ft)" field to match your specific product's coverage rate, found on the product packaging or manufacturer's specification sheet.

Where do I find my insulation's coverage per package?

This is printed on the product packaging, typically expressed in total square feet covered — enter the exact figure for your chosen R-value and product for an accurate estimate.

This calculator is provided for general informational and estimation purposes only. Results should not be treated as professional financial, tax, legal, medical, or engineering advice. Always verify critical calculations with a qualified professional or official source before making decisions.