Insulation Area Calculator
Every other insulation number starts with square footage. Enter your room dimensions and this figures the flat (attic/floor) area, the wall area, and the net area after you deduct doors and windows.
Your project
Covers cuts, compression and odd bays. 10% is the usual default.
Your results
- Flat area (attic / floor)
- 384 sq ft
- Gross wall area
- 640 sq ft
- Net wall area after openings
- 580 sq ft
- Order quantity with waste
- 638 sq ft of wall
- Wall perimeter
- 80 ft
422 sq ft if you're insulating the flat area too
Estimates use typical US material and labor pricing. Confirm quantities against the coverage chart on the bag before you buy.
Gear for this job
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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Staple Gun Insulation
Upholstery Staple Gun Heavy Duty, YEAHOME 4-in-1 Stapler Gun with 4000 Staples, Manual Brad Nailer Power Adjustment Stapler Gun for Wood, Crafts, Carpentry, Decoration DIY
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Arrow T50 Heavy Duty Staple Gun Kit with 3750 Pieces T50 Staples | All Chrome Steel Stapler with 3750 Pieces T50 1/4", 3/8", 1/2" Staples, for Upholstery Professional Projects
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Bielmeier Cordless Electric Staple Gun for Light-Duty Upholstery Craft DIY | Compact Handheld, Works on Fabric Softwood Cardboard, T50 STAPLES UP TO 3/8, Rechargeable Battery, Easy Load Quick Release
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How this calculator works
- Flat area = length × width
- Gross wall area = 2 × (length + width) × wall height
- Net wall area = gross wall area − door & window area
- Order quantity = net area × (1 + waste %)
Frequently asked questions
Should I deduct windows and doors from insulation area?
Deduct them from the amount you install, but it is normal to still buy the gross figure when the openings are small — offcuts get used in narrow bays and around boxes.
How much waste should I add for insulation?
10% is standard for batts in regular 16-inch bays. Go to 15% for irregular framing, cathedral ceilings or lots of obstructions.
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Flat area (attic / floor)
384 sq ft