Match your target R-value to the product label for the correct thickness.
MEASURE. ESTIMATE. BUILD.
Insulation Calculator
Enter the area you want to insulate to get the square footage of batts or rolls to buy, adjusted for framing.
01 / PROJECT DIMENSIONS↙
Total wall length
Wall height
Waste %%
Change any measurement to update your estimate.
02 / YOUR MATERIAL ESTIMATE
You need approximately
4 batt packages
covers 336 ft² (incl. waste)
- Area to cover
- 336 ft²
- Exact amount
- 3.81 batt packages
Field notes
Cut batts a hair long and friction-fit them — a batt that's compressed or gapped loses R-value fast, and a 5% trim allowance covers the fussy spots around outlets and blocking. Don't stuff a thick batt into a shallow cavity to hit a higher R; compressed insulation underperforms its label. Match the batt width to your actual stud spacing (16 vs 24 inch) before you order, not after.
How the insulation calculator works
The math behind the tool:
coverage ft² = area × (1 + waste%)
packages = coverage ÷ package coverageSources: ENERGY STAR (U.S. EPA & DOE) (recommended R-values by climate zone).
Frequently asked questions
How much insulation do I need?
Measure the area to insulate in square feet and divide by the coverage printed on the batt or roll package. Add about 5% for trimming around framing and outlets.
What R-value do I need?
ENERGY STAR — a joint U.S. EPA and Department of Energy program — recommends roughly R-13 to R-21 for walls and R-30 to R-60 for attics depending on your climate zone; check the ENERGY STAR R-value map for your area.
How do you calculate R-value?
R-values add in series, so layered insulation is the sum of each layer — R-19 batts under R-30 blown-in gives R-49. What you need depends on climate zone and location in the house; ENERGY STAR publishes recommended attic and wall values by zone.
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