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Est. Weight (lbs)
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Based on Insulation density (0.05 t/yd³)
Free Insulation Calculator
Insulation Calculator: Stop Guessing, Start Saving
Enter your area dimensions into the insulation calculator above and instantly see how many bags you need, which R-value to choose, and what it will cost in 2026.
Common Attic Sizes: Quick Bag Count
| 500 sq ft attic (R-19 batts) | 6 bags |
| 1,000 sq ft attic (R-19 batts) | 12 bags |
| 1,000 sq ft attic (blown-in R-30) | 25 bags |
| 1,500 sq ft attic (R-38 batts) | 18 bags |
Insulation Reference Guide
Insulation Costs in 2026
| Fiberglass batt bag (R-19) | $50 – $70 |
| Blown-in fiberglass bag | $35 – $50 |
| Spray foam (per board foot) | $1.50 – $3.00 |
| 1,000 sq ft attic (DIY batts) | $500 – $800 |
Prices are 2026 US averages. Actual costs vary by region and supplier.
Recommended Depths for Insulation
| Project / Use Case | Recommended Depth |
|---|---|
| Attic (cold climate) | R-38 to R-60 |
| Attic (moderate climate) | R-30 to R-38 |
| Walls (2×4 framing) | R-13 to R-15 |
| Walls (2×6 framing) | R-19 to R-21 |
How to Calculate Insulation Volume
Most landscaping suppliers sell insulation by the cubic yard. To convert your project area to cubic yards, use this formula:
Volume (cu yd) = (Length × Width × Depth) ÷ 27
Our calculator also multiplies your cubic yard result by 0.05 tons/yd³ (the standard density for insulation) to show estimated weight — essential if you are hauling the material yourself or need delivery pricing.
Insulation Calculator: R-Values and Coverage Explained
R-value measures thermal resistance. Higher R-values mean better insulation. A single bag of R-19 fiberglass batt (15 inches wide) covers 88 square feet at its rated thickness. Thicker batts (R-30, R-38) cover less area per bag because each batt is bulkier.
Blown-in insulation is sold by the bag and rated by installed depth. One bag typically covers 40 square feet at R-30 (about 10 inches deep). Always check the bag label for the coverage chart specific to your target R-value.
Pro Tips & Insights
1
Batt insulation is faster for open attics with standard joist spacing. Blown-in insulation is better for irregular spaces, around obstacles, and topping up existing insulation.
2
One bag of R-19 batt insulation (15-inch wide) covers approximately 88 square feet. One bag of blown-in fiberglass covers about 40 square feet at R-30 depth.
3
Do not compress batt insulation to fit tight spaces. Compressed insulation loses R-value. Cut batts to fit instead, or switch to blown-in for irregular cavities.
4
In 2026, the federal energy tax credit covers 30% of insulation material costs up to $1,200 per year. Keep your receipts.
Frequently Asked Questions
How many bags of insulation do I need for my attic?▼
Measure your attic floor area in square feet, then divide by the coverage per bag. For R-19 batts (88 sq ft per bag), a 1,000 sq ft attic needs 12 bags. For blown-in at R-30 (40 sq ft per bag), the same attic needs 25 bags. Our insulation calculator above handles the math.
What R-value insulation do I need?▼
The US Department of Energy recommends R-38 to R-60 for attics in most climates, R-13 to R-21 for walls depending on framing depth, and R-25 to R-30 for floors. Colder climates need higher R-values.
Is blown-in or batt insulation better?▼
Batt insulation is cheaper per square foot and easier for DIY in open areas with standard spacing. Blown-in insulation fills gaps better, works around obstacles, and is ideal for topping up existing insulation. Both perform similarly when installed correctly.
How much does attic insulation cost in 2026?▼
Batt insulation costs $0.50 to $1.00 per square foot installed (DIY: $0.30-$0.50). Blown-in insulation costs $1.00 to $2.00 per square foot professionally installed. A 1,000 sq ft attic typically costs $500-$2,000 depending on type and R-value.
Can I add new insulation over old insulation?▼
Yes, if the old insulation is dry, flat, and free of mold or pest damage. Lay new batts perpendicular to the old layer, or blow new insulation on top. Do not use faced batts over existing insulation (traps moisture).