Estimate batt packs or rolls from wall, attic, or floor area—subtract openings, add waste, and round up to whole packages.
Area to insulate
Total length of walls to insulate (sum of wall runs).
Doors, windows, hatches, and other areas you will not insulate.
Product & coverage
Presets are typical package coverages—always use the sq ft (or m²) printed on your product label for the chosen R-value.
Use 2+ when stacking layers for higher R-value.
5–10% for simple rooms; 10–15% for odd cavities.
Insulation needed
Cost estimate
Enter a pack price to estimate material cost (excludes labor and vapor barrier).
This tool estimates quantity only. Choose R-value from local energy code and climate zone, and confirm cavity depth so batts are not compressed.
Formula
How to Calculate
Examples
About this calculator
The Insulation Calculator estimates how many batt packs or rolls you need for walls, attics, and floors. Enter area or dimensions, subtract openings, apply layers and waste, then divide by the coverage printed on your insulation package.
Walls, attic/floor, or known area
Use wall run × height, length × width for attics and floors, or enter gross area directly when you already measured the space.
Batts and rolls
Pick batt packs or rolls, choose a common coverage preset or enter the exact sq ft (or m²) per package from the label, and set layers for stacked installs.
Waste-aware pack counts
Openings are subtracted, waste (default 10%) is applied, and results round up to whole packs so you do not under-order.
- Wall cavity batts
- Attic roll insulation
- Floor joist bays
- Material cost estimates
Frequently asked questions
Quick answers about this calculator—how it works, accuracy, and everyday use.
Measure the area to cover (wall run × height, or length × width for attics/floors), subtract doors, windows, and hatches, multiply by the number of layers, add a waste allowance (typically 5–15%), then divide by the coverage per pack printed on the product label. Round up to whole packs.
Use the square feet (or square meters) per package listed on the bag for your R-value and width. Common fiberglass packs often cover roughly 40–90 sq ft depending on thickness—presets in this calculator are only starting points.
Batts are pre-cut for stud or joist bays and suit walls and floors with regular framing. Rolls work well for open attic floors where you unroll and cut to length. Both are sold by coverage area, so the pack-count math is the same.
No. R-value depends on climate zone, assembly, and local energy code. This tool estimates how many packs to buy after you pick a product. Also check cavity depth so batts are not compressed, which reduces performance.