Insulation Calculator
Divide wall or attic area by batt coverage from the label, apply waste from 0 to 40 percent, and round up. R-value and compression stay on you. Estimate only, not a permit, code check, or engineered design.
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How to estimate insulation units
- Enter the area to cover in the same unit the package uses.
- Enter coverage per bag or batt package from the label.
- Set waste from 0 to 40 percent for cuts around openings.
- Read raw units and units to buy. Confirm R-value on the product, not here.
Insulation unit count
Area over package coverage with waste
| Raw units | area / battCoverage |
|---|---|
| Buy | ceil(raw × (1 + waste/100)) |
| Waste bound | 0 to 40 percent |
| Coverage source | Product label, not a fixed table |
| Omitted | R-value targets and blown-in density |
| Compliance | Estimate only. Compression changes performance. |
What this insulation count covers
Batts and bags that publish a coverage area. Blown-in pounds need a different model. Stud layout sits on studs. Wall sheets sit on drywall. Attic area helpers sit on square footage.
How units to buy are computed
raw = area / battCoverage. buy = ceil(raw × (1 + waste/100)). Waste stays from 0 to 40. Match area and coverage units, usually square feet.
Kraft face, unfaced, and cavities
Faced and unfaced packages list different coverages. Narrow cavities may need cut downs that raise waste. Spray foam and blown cellulose are outside this batt math.
Use cases
A 1000 sq ft attic at 40 sq ft per bag with 5% waste. Comparing two package coverages. Not an energy code checklist.
Limits
No R-value field and no climate zone table. Estimate only, not a permit, code check, or engineered design. See the disclaimer.