How Much Insulation Do You Need?
Enter your area and pick an application — get rolls or bags to buy for attics, walls, and floors, with the right R-value built in.
Last updated: June 1, 2026
Area to Insulate
Not sure? Batts/rolls for walls & floors · Blown-in for attics. Compare →
DOE recommends R-30 to R-60 for attics — pick higher R for colder climates. R-value guide →
Insulation Order Summary
31
bags to order
Target R-valueR-38
Area to Insulate1000 sq ft
Coverage per bag36 sq ft
Extra for Waste+3 bags (10%)
Total Coverage1116 sq ft
1000 sq ft · R-38 · blown-in · 10% waste included
Worked Examples
Attic — 1000 sq ft, Blown-in to R-30
- Area: 1000 sq ft · blown-in coverage at R-30: 46 sq ft/bag
- +10% waste: 1,100 ÷ 46 = ceil(23.9) = 24 bags to order
- Most home centers lend the blower free when you buy this many bags
2×4 Wall — 500 sq ft, Batts to R-13
- Area: 500 sq ft · R-13 batt coverage: 40 sq ft/roll
- +10% waste: 550 ÷ 40 = ceil(13.75) = 14 rolls to order
- R-13 to R-15 is the standard fill for 2×4 stud walls
Floor — 800 sq ft, Batts to R-19
- Area: 800 sq ft · R-19 batt coverage: 49 sq ft/roll
- +10% waste: 880 ÷ 49 = ceil(17.96) = 18 rolls to order
- R-19 batts fit between standard floor joists
Batts & Rolls vs Blown-in
| Batts & Rolls | Blown-in (loose fill) | |
|---|---|---|
| Best for | Walls, floors, open accessible spaces | Attics, irregular cavities, over old insulation |
| DIY difficulty | Easy — cut and fit by hand | Moderate — needs a rented blower |
| Gap coverage | Can leave gaps if cut poorly | Fills gaps and corners well |
| Tools needed | Knife, staple gun, straightedge | Blower machine (often lent free) |
DOE Recommended R-values
| Area | Warm Climate | Cold Climate |
|---|---|---|
| Attic | R-30 to R-49 | R-49 to R-60 |
| 2×4 Wall | R-13 | R-13 to R-15 |
| 2×6 Wall | R-19 | R-19 to R-21 |
| Floor | R-13 | R-25 to R-30 |
Recommendations vary by climate zone. Check your zone on the DOE or ENERGY STAR insulation map for exact targets.
Frequently Asked Questions
Measure the area you're insulating in square feet (length × width), pick your application (attic, wall, or floor), and choose batts/rolls or blown-in. Each package covers a set area at a given R-value — divide your area by that coverage and add 10% for waste. This calculator does it for you instantly.
The U.S. Department of Energy recommends R-30 to R-60 for attics, R-13 to R-15 for 2×4 walls, R-19 to R-21 for 2×6 walls, and R-13 to R-30 for floors. Higher R-values are recommended in colder climates. Select your application above to auto-fill the recommended R-value.
Batts and rolls are best for walls, floors, and open accessible spaces — easy to install by hand. Blown-in (loose-fill) is best for attics and hard-to-reach cavities — it fills gaps better but needs a rented blower machine. Many home centers lend the blower free when you buy enough bags.
A standard R-13 batt/roll package covers about 40 sq ft for 2×4 walls. Coverage drops as R-value rises because the insulation is thicker: R-30 attic batts cover about 31 sq ft per bag. Always check your specific product's bag label — coverage varies by manufacturer and width.
Usually no — you can add new insulation on top of old in an attic as long as the existing insulation is dry and not compressed or moldy. For walls, you'd only remove old insulation during a renovation. Remove and replace any insulation showing water damage, pests, or mold.
Batts and rolls run about $0.40–$1.50 per sq ft in materials; blown-in cellulose or fiberglass runs about $0.30–$1.00 per sq ft. A 1,000 sq ft attic to R-38 costs roughly $400–$900 in materials for a DIY install. Enable cost estimate in Advanced settings for your specific count.