Floor Insulation Calculator
Insulating a floor over an unheated space is the fastest fix for cold feet. Enter the footprint and joist layout for bay counts and batt quantities.
Your project
Covers cuts, compression and odd bays. 10% is the usual default.
Your results
- Floor area
- 720 sq ft
- Joist bays
- 18 bays
- 8 ft batts required
- 82 pieces
- R-value achieved
- R-29.6
- Recommended for your zone
- R-30
- Support rods needed
- 246 rods
- Material cost
- $952
Each about 30 ft long
R-0.4 short
About one every 16 in along each bay
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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Insulation Support Rods
200 Pcs 16 Inch Insulation Support - 16" Carbon Steel Metal Insulated Wire for Attic, Ceiling Insulation, DGG005
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Insulation Support Wire 16 Inch, 50 PCS Spring Steel Insulation Rods for 16" On-Center Joists, Heavy-Duty Flexible Batt Insulation Supports for Attic, Ceiling & Wall
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U0U 16 Inch Insulation Support Wire,30 Pcs Insulation Hangers Bracket Metal Support Rods,Stainless Steel Metal Insulated Wire for Attic,Garage,Ceiling Insulation (30, 16inch)
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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
- Floor area = length × width
- Bays = width in inches ÷ joist spacing
- Batts = area × (1 + waste %) ÷ area per batt
Frequently asked questions
Which way does the paper facing go on floor insulation?
Facing toward the heated side — that means up, against the subfloor. In humid southern climates unfaced batts are often the better choice.
How do I hold floor batts up?
Wire support rods (lightning rods) every 16 inches, or house wrap stapled across the joists. Never rely on friction — batts sag and lose their R-value once there's a gap.
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Floor area
720 sq ft