Insulation Calculator
Calculate insulation material and cost for fiberglass batt, blown-in, or spray foam by R-value target.
By Konstantin Iakovlev · Updated April 2026 · Source: HomeAdvisor
Total Project Cost
$420.00
Est. Annual Savings
$300.00
Payback Period
1.4 years
Project Details
| Total Area | 400 sq ft |
| Fiberglass Batt (R-19) | 10 rolls |
| Cost per sq ft | $0.55 |
| Material Cost | $220.00 |
| Labor Estimate | $200.00 |
| Total Project Cost | $420.00 |
Energy Savings Estimate
| Estimated Annual Energy Savings | $300.00 |
| Payback Period | 1.4 years |
| 5-Year Net Savings | $1,080.00 |
| 10-Year Net Savings | $2,580.00 |
Use the Insulation Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.
Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.
How It Works
Estimating how much fiberglass batt, blown-in cellulose, or spray foam you need to hit a target R-value comes down to a few measurable inputs. With energy costs projected to climb roughly 4.5% annually through 2026, tightening up a home's thermal envelope is one of the more reliable ways to cut bills and shrink a carbon footprint.
Sizing starts by dividing your target R-value by the R-value per inch of the insulation type you choose, which yields the thickness required. Multiplying that thickness by the area produces a total volume, then converts into the units you actually buy, whether square feet of batts, bags of blown-in, or board feet of spray foam, and applies the 2026 average material cost per unit.
Check what is already in place first, since existing insulation often means you only need to top it up rather than start over. Square footage is easy to undercount once joists and irregular bays enter the picture, so measure carefully. These figures cover materials only, and bringing in a crew can add 30-50% to the bottom line.
Example: Insulating a 1,500 sq ft Attic with Blown-in Cellulose
- 1 Input: Attic Area = 1,500 sq ft, Desired R-value = R-49 (common for 2026 energy codes), Insulation Type = Blown-in Cellulose (R-value per inch = 3.7).
- 2 Calculation: Required thickness = R-49 / 3.7 R/inch = 13.24 inches. Total volume = 1,500 sq ft * 13.24 inches * (1 ft / 12 inches) = 1,655 cubic feet. Assuming 3.5 lbs/cubic foot density, this is 5,792.5 lbs. A 30 lb bag of blown-in cellulose covers approximately 11.5 cubic feet at R-49. So, 1,655 cubic feet / 11.5 cubic feet/bag = 144 bags.
- 3 Intermediate Result: You will need approximately 144 bags of blown-in cellulose.
- 4 Final Result: With the average 2026 cost of blown-in cellulose at $38.50 per 30 lb bag, the estimated material cost for this project is 144 bags * $38.50/bag = $5,544.00. This doesn't include potential equipment rental (around $150/day) or professional installation.
Source: HomeAdvisor · Last updated: April 2026
Frequently Asked Questions
What R-value insulation do I need?
What type of insulation is the most cost-effective?
How much money does insulation save on energy bills?
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