Insulation R-Value Calculator
Based on DOE recommendations by climate zone. Enter your climate zone and surface type to get the recommended R-value, insulation type options, batt/roll count, and cost estimate.
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Top PickR-13 Kraft Faced Batts — Home Depotfrom $16.98/bag* Affiliate links — we may earn a commission at no cost to you.
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How to Use This Calculator
- 1Enter your measurements in the fields above. Use the units shown next to each field (ft, in, etc.).
- 2Click Calculate to get your material estimate instantly.
- 3Review the highlighted result — it shows the key quantity you need to order.
- 4Use Copy Results to save your estimate, or bookmark the URL — your inputs are encoded in the link.
Pro tip: Always add 10% to your material order to account for waste, cuts, and defects.
Frequently Asked Questions
What R-value do I need in my attic?
The DOE recommends R-38 to R-60 for attics in most of the US. In warmer climates (Zone 1–3), R-30 to R-38 is sufficient. In cold climates (Zones 5–8), aim for R-49 to R-60. More insulation always reduces energy bills.
What is the R-value of a 2×4 wall?
A 2×4 wall cavity (3.5" deep) holds R-13 or R-15 batts. Adding 1" rigid foam sheathing outside adds another R-5 to R-6, for a total assembly R-value of about R-18 to R-21.