Attic Insulation Calculator
Enter your attic footprint and what's already up there. This works out the extra depth needed to reach your target R-value, how many bags or batts that takes, and what it should cost.
Your project
Old blown fiberglass ≈ 2.5, cellulose ≈ 3.2, old batts ≈ 3.0
Covers cuts, compression and odd bays. 10% is the usual default.
Your results
- Target R-value
- R-60
- Existing R-value
- R-10
- Additional depth to add
- 20 in
- Bags required
- 52 bags
- Estimated material cost
- $1,584
- Installed cost (pro)
- $2,604
Climate zone 5
25.4 sq ft per bag at this depth
Material plus typical contractor labor
Estimates use typical US material and labor pricing. Confirm quantities against the coverage chart on the bag before you buy.
Gear for this job
Blown In Cellulose Insulation
Owens Corning R-19 Unfaced Fiberglass Insulation 77.5 Sq.ft (15 in x 93 in) 1 Batt
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Attic Measuring Rulers (Case of 400), 20 Inch, Card Stock, Attic Insulation R-Value Ruler for Insulators Ceiling Insulation
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DGSL Double Reflective Bubble Foil Insulation Foam, 23.6 in X 10 FT Aluminum Foil Thermal Insulation Radiant Barrier for Window, Garage Door, RV, Roof
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Attic Ventilation Baffles
36 Pcs Attic Insulation Baffles for 24" Rafter Bays, 2" Air Channel | Black Polyethylene Rafter Vents,Improve Roof Ventilation,Prevent Insulation Blockage,Hassle-Free Installation
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UDV2248 Durovent Foam Attic Rafter Vent (Pack of 70) by ADO Products
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30 Pack 24 Attic Insulation Baffle, Sturdy Polypropylene Attic Baffles for 24" On-Center Rafter Bays with 2" Air Channel, Improve Roof Ventilation and Prevent Insulation Blockage
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Respirator Mask Insulation Work
Respirator Mask with Filters set - Reusable Respirator Mask for Chemicals, Painting, Spraying, Epoxy Resin, Dust, DIY etc
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Full Face Organic Vapor Respirator - Protective Eye & Nose Shield with Anti-Fog Heavy Duty Lens & Adjustable - Chemical, & Particulate Respirator. Includes 2 Filter Cartridges - Industrial Grade
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Reusable Half Facepiece, Half Facepiece with Goggle, Protection from Dust and Organic Vapors, for Painting, Sanding, Polishing, Spraying, Decorating
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How this calculator works
- Existing R = existing depth × R-per-inch of what's up there
- R needed = target R − existing R
- Depth to add = R needed ÷ R-per-inch of new material
- Bags = (R needed × area) ÷ bag coverage rating, then add waste
Frequently asked questions
Can I add new insulation over old insulation?
Yes, as long as the old material is dry and not mouldy. Never lay faced (paper or foil backed) batts over existing insulation — the facing traps moisture. Use unfaced batts or blown-in.
How many inches is R-49?
About 14 inches of blown fiberglass, 14 inches of cellulose, or 13 inches of high-density batts. Loose-fill bags list a coverage chart on the side — follow it.
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Additional depth to add
20 in