Insulation coverage formula
net area = length × height × surfaces − openingspackages = net area × allowance ÷ package coveragePackage quantity always rounds up so partial packages are not treated as purchasable units.
Insulation calculator
Estimate square footage and full packages of batts or rolls for equal walls, ceilings, or attic sections.
Enter the coverage area
Calculate different wall or ceiling sizes separately, then add the package counts.
Coverage and cavity fit are separate checks
Package coverage estimates quantity, but the insulation still has to match cavity width, depth, framing, and the required thermal assembly. Compressing a batt to force a fit can change performance.
- Subtract openings only when their framing does not consume replacement pieces.
- Use the package's actual coverage and piece dimensions.
- Account separately for rim joists, headers, odd cavities, and access areas.
Match the assembly
Cavity depth, stud or joist spacing, climate zone, air sealing, vapor control, and local energy requirements determine which product is appropriate. This calculator estimates quantity, not the required insulation specification.