Insulation Batt Coverage and Count
Batts and bags from the net cavity area / coverage per batt and per bag, at a waste allowance.
Example
You enter
- Net cavity area (ft², less openings) 500
- Coverage per batt (ft², e.g. 9.69 for an R-13 15 x 93 in batt) 9.69
- Coverage per bag (ft², from the label) 125.94
You get
- Batts (pieces) 52
- Bags 4
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Scope500 ft^2, R-13 15 x 93 in batt (9.69 ft^2), 125.94 ft^2/bag (Owens Corning) -> 52 batts, 4 bags; a deeper R-15 bag covering 67.81 ft^2 raises it to 8 bags for the same wall. Count the batts to confirm a full fill. The label coverage governs.
Formula or tablenet = area x (1 + waste%); batts = ceil(net / coverage_per_batt); bags = ceil(net / coverage_per_bag).
Source and editionBatt insulation takeoff from the manufacturer's label coverage per batt and per bag, by name.
Free accessThe area-over-coverage takeoff is public arithmetic; the coverage per batt and per bag come from the manufacturer's label.
What governsEstimate. AHJ and licensed professional govern.
API field namesarea_ft2, coverage_per_batt, coverage_per_bag, batts, bags
- Net area cavity area less openings, times the waste allowancetakeoff practice
- Counts batts = ceil(net / coverage per batt); bags = ceil(net / coverage per bag)arithmetic
- Label coverage coverage per batt/bag from the manufacturer's labelscope of this tile