Free insulation calculator estimates rolls, batts or blown-in bags for attics, walls and floors based on your target R-value, with coverage and cost.
This calculator sizes insulation for the home - fiberglass rolls or batts laid between attic joists or in wall and floor cavities, or loose-fill blown-in bags for attics. What matters for comfort and energy bills is the R-value, how strongly the material resists heat flow, so the tool works from a target R-value.
Enter the area, location (attic, wall or floor), target R-value and product coverage. The result shows the rolls or bags to buy and the cost, and the FAQ lists common R-value ranges so you can pick a sensible target.
Recommended R-values vary by climate zone - in the US, attics typically need R-38 to R-60, walls R-13 to R-21 and floors R-19 to R-30 (US DOE guidance). The location selector is informational; enter the R-value your product label specifies and the coverage per roll matches that product.
Heat rises, so the attic is the biggest single source of heat loss in most homes - codes and energy guides therefore call for much higher R-values there. The coverage per roll shrinks as R-value (thickness) increases, which is why the calculator takes coverage per roll as input.
About 10% is typical to cover odd cavities, joist bays and cutting mistakes. Batt and roll insulation is easy to cut, but underestimating means a second trip and a partial roll you cannot easily return.