Insulation Calculator
Calculate how much insulation you need by type, R-value, and area. Get quantity estimates and costs for batts, rolls, blown-in, and spray foam.
How It Works
This calculator estimates how much insulation material you need based on the area to cover and the type of insulation selected.
Batts & Rolls: Total area ÷ coverage per unit (sq ft per batt or roll), rounded up.
Blown-in: Coverage per bag varies by target R-value. Higher R-values require thicker application, so each bag covers fewer square feet.
Spray Foam: Measured in board feet (1 sq ft × 1 inch thick). Total board feet = area × thickness in inches. Closed-cell foam provides roughly R-7 per inch.
Cost estimates are averages that include materials and typical installation labor. Actual costs vary by region and contractor.
Frequently Asked Questions
What R-value insulation do I need?
R-value requirements depend on your climate zone and where you are insulating. Attics typically need R-38 to R-60. Exterior walls need R-13 to R-21. Floors over unheated spaces need R-19 to R-30. Check the DOE climate zone map or local building codes for your area's requirements.
What is the difference between batts, rolls, and blown-in insulation?
Batts are pre-cut rectangles that fit between standard stud or joist spacing. Rolls are continuous lengths you cut to size. Blown-in is loose fill pumped into attics or wall cavities with a blower machine. Batts and rolls are easiest for DIY wall projects; blown-in is best for attics and retrofit jobs.
How much does insulation cost to install?
Fiberglass batts run $0.50-$0.80 per sq ft installed. Blown-in cellulose costs $0.75-$1.00 per sq ft. Closed-cell spray foam is the most expensive at $1.50-$2.00+ per sq ft, but offers the highest R-value per inch and doubles as an air and vapor barrier.
Can I install insulation myself?
Fiberglass batts and rolls are the most DIY-friendly. Blown-in requires a blower machine (often available free with purchase from home improvement stores). Spray foam requires specialized equipment and is best left to professionals for large areas.
Should I remove old insulation before adding new?
Not necessarily. If existing insulation is dry and in good condition, you can add new insulation on top for additional R-value. Remove old insulation if it is water-damaged, moldy, compressed, or contaminated with pests. Blown-in cellulose or fiberglass works well layered over existing batts in attics.