Default batt is R-13 kraft 15×93×3.5 in from the Owens Corning EcoTouch product data sheet. Bag coverage is Home Depot BF10’s 11 pieces times that batt face — 106.56 sq ft — labelled HD bag × OC batt size. It is not the 125.94 sq ft figure some 11-batt listings still print.
Basket 2026-08-27
Room and batts
Bags to buy
4 bags
3.603 exact · 349 sq ft net · 106.56 sq ft/HD bag × OC batt size
Cost: enter a local price to see a dollar total. We will not invent one.
Gross walls
384 sq ft
Doors + windows
−35 sq ft
OC batt face
9.6875 sq ft (15×93×3.5 in)
HD BF10 pieces
11
HD bag × OC batt size
106.56 sq ft/bag
After 10% convention
383.9 sq ft
Default batt is R-13 kraft 15×93×3.5 in from the OC EcoTouch PDS. Bag coverage is 11 × 9.6875 = 106.56 sq ft, never 125.94.
What calculator.net does not show
Geometry sites divide wall area by a round 100 or by a bag label of 125.94. Thirteen 15×93 batts would be 125.94 sq ft. Home Depot’s BF10 bag is 11 pieces. Eleven times 9.6875 is 106.56. This page multiplies the piece count you can count on the bag by the batt size on the OC sheet, then says so on the result line.
National online bag dollars were not pinned for this index. The price field starts empty. 10% extra is a calculator convention for cuts, not an Owens Corning waste percent.
Worked US example: 12×12 room, 8 ft walls
1 average door, 1 average window, ceiling off, 10% convention. R-13 kraft 15×93×3.5 in, BF10.
Batt face = (15/12) × (93/12) = 9.6875 sq ft
HD BF10 bag = 11 pieces
Coverage = 11 × 9.6875 = 106.56 sq ft/bag (HD bag × OC batt size)
not 125.94
Gross walls = 2 × (12 + 12) × 8 = 384 sq ft
Openings = 20 + 15 = 35 sq ft
Net = 349 sq ft
With 10% = 349 × 1.10 = 383.9 sq ft
Exact bags = 383.9 ÷ 106.56 = 3.603 → buy 4 bags
Cost = $ null until you type a local price
Citations
Owens Corning. EcoTouch PINK Fiberglas Insulation product data sheet. Accessed 2026-08-27. https://www.owenscorning.com/dms/10013811 — September 2020. R-13 kraft-faced wood-frame batt is listed at 15 in width, 93 in length, 3½ in thickness. Face area = (15/12)×(93/12) = 9.6875 sq ft. This sheet does not set bag piece count.
The Home Depot. Owens Corning R-13 kraft faced batt 15 in × 93 in, model BF10. Accessed 2026-08-27. https://www.homedepot.com/p/Owens-Corning-R-13-Kraft-Faced-Fiberglass-Insulation-Batt-15-in-x-93-in-BF10/202676829 — Model BF10. Home Depot copy and Q&A: 11 pieces per package. Coverage used here is 11 × 9.6875 = 106.56 sq ft/bag, labelled HD bag × OC batt size. Some distributor listings print 125.94 sq ft on an 11-batt 15×93 bag (that is 13 × 9.6875) — this calculator never uses 125.94.
These calculators estimate material takeoff for planning. They are not engineering, structural, or code advice. Confirm spans, mixes, fastener schedules, and permits with a licensed professional and the manufacturer’s current data sheet. Local shelf prices and tax are not this index.