Batts and rolls

Insulation Calculator

Estimate insulation packages using net cavity area and package coverage. Enter the job dimensions below, then review the guide before ordering.

Insulation calculation formula

net cavity area / package coverage x allowance = packages

Worked example: A 900 sq ft net cavity area with packages covering 88 sq ft requires 10.23 packages. With 5% extra, the result is 10.74, so purchase 11 packages.

Use net cavity area

Measure wall and ceiling areas and subtract large openings where appropriate. Separate assemblies by cavity depth, framing spacing, and required R-value because those conditions may require different products.

Read the package coverage

Packages that look similar may cover different areas. Use the exact coverage printed for the selected width, thickness, and R-value. Do not substitute nominal package dimensions for the manufacturer's coverage statement.

Installation quality matters

Compression, gaps, voids, and poorly fitted pieces reduce performance. Follow manufacturer instructions for vapor retarders, ventilation clearances, electrical boxes, and protective equipment.

Before placing an order

Recheck field measurements, confirm the selected product's actual package coverage or density, and ask the supplier about order increments, minimum quantities, delivery limits, and return rules. Keep unlike products and assemblies in separate calculations.