Enter the area you're insulating and the coverage per package to find out how many bags, rolls, or batts you need — with a waste factor and total cost.
Insulation is sold by coverage area at a given R-value, so the math is simple: area to insulate ÷ coverage per package, rounded up, plus a little waste. The catch is that coverage depends on the R-value you pick — the higher the R-value, the thicker the layer, and the fewer square feet each bag, roll, or batt covers. Always read the coverage off the package for your target R-value and enter it above.
1. Area = the surface you're insulating (attic floor, wall area, etc.).
2. With waste = area × (1 + waste % ÷ 100).
3. Packages = area with waste ÷ coverage per package, rounded up.
| Where | Typical R-value | Notes |
|---|---|---|
| 🏠 Attic | R-38 to R-60 | Biggest energy savings |
| 🧱 Exterior walls | R-13 to R-21 | Depends on stud depth |
| 🪵 Floors | R-25 to R-30 | Over crawlspaces |
| 🏚️ Basement walls | R-11 to R-15 | Below grade |
Batts and rolls are pre-cut or continuous fiberglass that you fit between studs and joists — easy for walls and open floors. Blown-in (loose-fill) is best for attics and hard-to-reach cavities, sold by the bag with a coverage chart for each R-value. Pick the type above and the wording updates so the count makes sense for your job.
The right R-value depends on where you live — colder climates need more. The U.S. Department of Energy publishes recommended R-values by climate zone, and local building codes set minimums. Insulating to (or above) the recommended level is one of the highest-return home upgrades you can make.