Insulation Calculator
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· Free
Enter your area and location to find out how many bags or rolls of insulation you need to reach the recommended R-value. Covers attics, walls, crawlspaces, and basements.
1. Area to insulate
2. Location
3. Insulation type
(recommended: R-49)
Your Insulation Estimate
30
bags (30 lb)
13.6"
depth needed
Calculation breakdown
Area: 800 sq ft
Target R-value: R-49
R per inch (Blown-in): 3.6
Depth needed: R-49 ÷ 3.6/inch = 13.6 inches
Units: 800 sq ft ÷ 30 sq ft/unit × 1.10 = 30 bags (30 lb)
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Recommended R-values by zone
| Location | Cold (Zones 5–8) | Mild (Zones 3–4) |
|---|---|---|
| Attic | R-49 to R-60 | R-38 to R-49 |
| Walls (2×4) | R-15 to R-21 | R-13 to R-15 |
| Crawlspace | R-25 to R-30 | R-19 to R-25 |
| Basement walls | R-15 to R-19 | R-11 to R-15 |
Source: DOE / IECC recommendations. Check local building codes for required minimums.