Insulation Calculator
Estimate insulation bags needed by area and R-value for walls or attics.
Bags needed
7 bags
- Area with 10% waste
- 550 sq ft
- Coverage per bag
- 88 sq ft
How we calculate this
Bags needed = (area × waste factor) ÷ coverage per bag, where coverage per bag depends on the R-value: higher R-values use thicker batts with lower coverage per bag.
Example
Measuring tips
Measure the total square footage of the area being insulated. For walls, use R-13 (2×4 framing) or R-19 (2×6 framing); for attics, R-30 or R-38 is standard in most US climate zones — check your local building code for the recommended minimum.
Common mistakes
- Using wall-rated batts (R-13/R-19) in an attic, which falls short of code minimums.
- Not accounting for obstructions like recessed lights, vents and joists when measuring.
- Compressing batts to fit a shallower cavity, which reduces their effective R-value.
Frequently asked questions
What R-value insulation do I need for my attic?
Most US climate zones recommend R-30 to R-49 for attics. Check your local energy code — colder climates generally require higher R-values.
How many bags of insulation do I need per 1,000 sq ft?
At R-30 (60 sq ft of coverage per bag), roughly 17-18 bags per 1,000 sq ft before waste. Use the calculator above for your exact R-value and area.
Related calculators
Estimates are provided for planning purposes. Actual material requirements may vary based on supplier specifications, compaction, site conditions, installation method, waste, and local code.