Batt & Roll Insulation Calculator
Batts come in bags rated by square feet of coverage. Tell this calculator the area and the bag size you're buying and it returns pieces, bags and total spend.
Your project
Covers cuts, compression and odd bays. 10% is the usual default.
Your results
- Coverage to buy
- 880 sq ft
- Individual batts
- 91 pieces
- Bags to buy
- 11 bags
- Estimated cost
- $682
- Cost per sq ft
- $0.77
9.69 sq ft each
Estimates use typical US material and labor pricing. Confirm quantities against the coverage chart on the bag before you buy.
Gear for this job
Fiberglass Batt Insulation R19
Owens Corning R-19 Unfaced Fiberglass Insulation 77.5 Sq.ft (15 in x 93 in) 1 Batt
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Owens Corning R-19 Fiberglass Batt Insulation Fits 2x6 Floor or Walls a Total of 10 Bags and Square Footage of 775 FT
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Owens Corning R-19 Unfaced Fiberglass Insulation 128-sq ft (24-in W x 96-in L)
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Rockwool Safe N Sound
3 pk 12"x12"x2" Rockwool ProRox Mineral Wool, Replaces Owens Corning Thermafiber, BMW211-3PK-NA
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10 pk 24" x 24" x 1" Rockwool ProRox Mineral Wool, Replaces Owens Corning Thermafiber, BMW122-10PK
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GlikCeil Acoustic Rock Wool Insulation, 2 Inch Thick | Soundproofing Material for Recording Studio, Home Theater, Apartment, Basement Walls and DIY Sound Absorption Projects
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Insulation Knife Cutter
Insulation Knife with Measuring Scale, Stainless Steel Double-Sided Serrated Insulation Cutter Tool with Nylon Sheath for Rockwool, Foam, Fiberglass, Drywall, Lawn and Garden
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Goldblatt 8" Rockwool Insulation Knife, Sod Cutter Tool for Fiberglass | Sod Knife, Double-sided Wavy Serrated Stainless Saw, Hammer-end Grip, for Rockwool, Foam, Styrofoam & Pipe Insulation
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Insulation Knife - Sod Cutter Knife: stainless steel 11.14-Inch sharp blade, double side utility Lawn Repair Saw with Nylon Sheath
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How this calculator works
- Coverage to buy = area × (1 + waste %)
- Pieces = coverage ÷ (batt width × batt length)
- Bags = coverage ÷ coverage per bag, rounded up
Frequently asked questions
How many square feet is a bag of insulation?
It varies by R-value: an R-13 bag typically covers 88 to 106 sq ft, while an R-30 bag covers around 40 to 58 sq ft. The number is printed on the front of the bag.
Do batts need to be cut to fit?
Yes — split batts around wiring rather than compressing them, and trim narrow bays about half an inch wide so the batt friction-fits without folding.
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Coverage to buy
880 sq ft