Attic Insulation Calculator - Calculate insulation needed for attic energy efficiency

Before making a decision based on estimates, run the numbers through this Attic Insulation Calculator. A few seconds of input can save hours of uncertainty. Start by filling in attic floor area, current r-value, target r-value, climate zone, insulation type, fiberglass batts, blown fiberglass, blown cellulose and spray foam. Based on these values, the tool computes additional r-value needed, insulation thickness, bags/rolls needed and other key metrics. People frequently need to calculate insulation needed for attic energy efficiency but lack a quick way to do it — this tool fills that gap.

Measure twice, order once — re-measuring saves far more than the few minutes it costs. Knowing the math behind a project helps you evaluate contractor quotes and catch mistakes. Depends on climate zone: Zone 1-2: R30-49, Zone 3-4: R38-60, Zone 5-8: R49-60. Paint coverage ≈ total wall area (length × height × number of walls minus openings) ÷ coverage per gallon. Material waste factors (typically 5-15%) should be added on top of the theoretical amount. Results are rounded for display; the underlying computation retains full precision.