Batt Insulation Calculator
Batts and whole bags from square feet and package dimensions.
How it works
Net square footage is the gross surface less openings. It is multiplied by layers and waste, then divided by one batt. Batts are rounded up before they are grouped into whole bags, matching the package-based estimating method used by US manufacturers.
The profiles use current US package examples, but SKU availability changes with R-value, facing and region. Replace width, length, thickness and pieces per bag with the exact label. The calculator estimates purchase quantity only; use your local energy code and assembly design to choose the required R-value.
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How the Batt Insulation Calculator works
This US batt insulation calculator converts square feet into individual batts and whole bags. Its profiles use American R-value labels, framing widths and current US package counts rather than converting a metric mineral-wool pack.
US batts match framing bays
The 15 in profiles are intended as quantity examples for framing at 16 in on center, while the 23 in profile fits the wider cavity associated with 24 in framing. Actual clear cavity width, product facing and assembly requirements still control the selected batt.
The current Knauf EcoBatt table lists an R-13 batt at 3½ × 15 × 93 in with 12 pieces and 116.25 ft² per bag, an R-19 batt at 6¼ × 15 × 94 in with 10 pieces and 97.92 ft², and a 23 × 93 in R-13 batt with 11 pieces and 163.40 ft².
Bag rounding follows batt rounding
Net square footage is multiplied by layers and the allowance, then divided by one batt. The batt count is rounded up before it is divided by batts per bag. That is why the result may be one bag higher than a quick area-only division near a boundary.
Package availability varies by region, facing and R-value. Use the profile as a worked example, then enter all four dimensions from the exact bag label. The ordered-coverage result shows how much material the rounded bags actually contain.
Quantity is not an R-value recommendation
The calculator reports installed thickness and volume, but it does not add R-values or decide whether R-13, R-19 or another assembly complies. Compression, gaps and a poor fit can reduce installed performance even when the nominal amount is correct.
Choose thermal resistance from the applicable local energy code and the complete wall, floor or attic design. Once that product is chosen, the calculator answers the narrower purchasing question: how many batts and full bags are required.
FAQ
How many bags of R-13 batts cover 600 sq ft?expand_more
With ten percent waste, 600 sq ft becomes 660 sq ft. A 15 × 93 in batt covers 9.6875 sq ft, so 69 batts are required. At 12 batts per bag, round up to 6 bags containing 697.5 sq ft.
Should I use 15 in or 23 in batts?expand_more
Use the width made for the actual clear framing cavity: 15 in batts are a common fit for 16 in on-center wood framing and 23 in batts for 24 in on-center framing. Verify the assembly, framing material and package label rather than choosing on area alone.
Does this calculator determine the R-value I need?expand_more
No. Required R-value depends on climate zone, local code and the complete building assembly. Select a compliant product first, then enter that product's dimensions and bag count to estimate purchase quantity.