Total Batts Needed
22
Area
860.0 sq ft
Rolls
3
Cost
$11.00
Higher R-value = better insulation
Standard: 15" or 23"
Standard: 40 sq ft
22
3
860.0 sq ft
$11.00
R-R-13 insulation at $0.01 per sq ft
Inputs
Result
Wall area = 2 × (20 + 15) × 8 = 560 sq ft. Ceiling = 20 × 15 = 300 sq ft. Total = 860 sq ft. Batts = ceil(860 / 40) = 22 batts. Rolls = ceil(22 / 10) = 3. Cost = 22 × $0.50 = $11.00.
Inputs
Result
Wall area = 2 × (24 + 24) × 10 = 960 sq ft. Ceiling = 24 × 24 = 576 sq ft. Total = 1,536 sq ft. Batts = ceil(1536 / 40) = 39 batts. Rolls = ceil(39 / 10) = 4. Cost = 39 × $0.75 = $29.25.
Calculate total wall area (perimeter × height) plus ceiling area. Divide by batt coverage (typically 40 sq ft per batt). Add 10% waste for cuts and fitting around obstacles.
R-value requirements vary by climate zone. Attics: R-30 to R-60, Walls: R-13 to R-21, Floors: R-19 to R-30. Check local building codes for specific requirements.
Standard batt widths are 15" (for 16" OC studs) or 23" (for 24" OC studs). Standard length is 93" (7.75 feet). Each batt typically covers 40 square feet.
Standard insulation rolls contain 10 batts. Each batt covers approximately 40 square feet, so one roll covers about 400 square feet.
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Last Updated: Feb 12, 2026
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