The square footage in a roll of insulation varies widely by R-value, thickness, width, and brand, so there is no single answer. For common residential fiberglass rolls sold at Home Depot and Lowe's, the coverage is printed on the bag. An R13 kraft-faced fiberglass roll, which is 3.5 inches thick for 2x4 walls, typically comes 15 inches wide by 32 feet long, covering 40 square feet, or 23 inches wide by 32 feet long covering about 61.33 square feet. An R19 roll for 2x6 walls or floors is thicker at 6.25 inches, so the roll is shorter to keep the bag manageable, often 15 inches by 22 feet covering 27.5 square feet, or 23 inches by 22 feet covering 42.17 square feet. An R30 roll, which is 9.5 inches thick for attics and 2x10 floors, might be 15 inches by 22 feet covering 27.5 square feet. Owens Corning Pink Next Gen and Johns Manville rolls follow similar sizes. Blown-in insulation is not sold as a roll, but bags list coverage. For example, one bag of Johns Manville Climate Pro blown-in fiberglass covers about 60 to 70 square feet at R19 and about 30 square feet at R38. Always check the label for net coverage, and buy 10 percent extra for waste and framing.
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