Insulation Calculator
Enter your climate zone, attic area, and existing insulation level to get the DOE-recommended R-value and the number of bags or board-feet of material you need. Results update instantly — no sign-up required.
Your Home Details
Recommended R-values from ENERGY STAR / U.S. DOE — as of June 2026. Bag coverage is a planning estimate; always check the coverage chart printed on your specific product bag before purchasing.
Material Comparison — Your Zone & Area
| Material | R/inch | Depth needed | Quantity |
|---|
How the formula works
Step 1 — Additional R needed:
additional_R = max(0, recommended_R − existing_R)
Step 2 — Depth of new insulation (inches):
depth_in = additional_R ÷ R_per_inch
Step 3a — Blown-in bags:
volume_cuft = (area_sqft × depth_in) ÷ 12
bags = ⌈volume_cuft ÷ cuft_per_bag⌉
Step 3b — Spray foam board-feet:
board_feet = area_sqft × depth_in
(1 board-foot = 1 sq ft at 1 inch thick)
More Insulation Calculators
- Attic Insulation Calculator — depth + bags for attic upgrades
- Blown-In Insulation Calculator — cellulose or fiberglass bags
- R-Value Calculator — standalone R-value lookup by zone
- Spray Foam Calculator — open-cell and closed-cell board-feet
- DOE Climate Zone Reference — find your zone + R-value table
- Insulation Guide — how to read the results
Frequently Asked Questions
The U.S. is divided into 8 climate zones. Zone 1 covers the hottest areas (Hawaii, southern Florida, Puerto Rico) and Zone 8 covers Alaska. Most of the continental U.S. falls in Zones 2–6. See our Climate Zone reference page or visit energy.gov for an interactive map.
For Zone 5 with no existing insulation, the DOE recommends R-49. Using blown-in cellulose (R-3.7/in), you need about 13.2 inches of depth. That is roughly 177 cu ft of settled material, which works out to approximately 216 bags of a standard 25 lb cellulose product. Always check the coverage chart on the specific bag you buy — coverage varies by manufacturer.
R-value measures how well a material resists heat flow. The higher the R-value, the better the insulation. The U.S. Department of Energy publishes recommended minimum R-values by climate zone. For attics, the recommendations range from R-30 in the warmest zones to R-60 in the coldest zones (as of June 2026).
Yes. R-values are cumulative. If you have existing R-11 batts and your zone recommends R-49, you only need to add R-38 of new material. Enter your existing R-value into the calculator and it will compute only the additional depth and bags required.
Completely free, no sign-up required. All calculations run in your browser — nothing you enter is sent to any server or stored anywhere.