House Wrap Calculator: Rolls Needed & Total Wall Area
Turns your wall dimensions into the rolls of house wrap to buy, with total wall area and a lap allowance built in.
rolls = ceil(1,540 ÷ 900) = 2
How it works
House wrap is the weather-resistive barrier that goes on the sheathing before the siding. It rolls out horizontally around the building, and sizing it is a matter of wall area divided by roll coverage.
The wall area is the perimeter of the house times the wall height. A 40 by 30 foot house has a 140-foot perimeter, so at 10 feet tall that is 1,400 square feet to cover. Unlike siding, you do not deduct the windows and doors: wrap is run continuously across the whole wall and the openings are cut out afterward, then taped. Running it long and cutting back is faster and gives a better seal than piecing it around each opening.
Roll coverage depends on the size you buy. The standard roll is 9 feet tall by 100 feet long, which is 900 square feet — one roll wraps a full story around a small house. There are also 3-foot rolls at 300 square feet for tight spots and taller 150-foot rolls at 1,350 square feet. The calculator adds a small allowance for the vertical and horizontal laps — usually 6 inches at seams — then rounds up to whole rolls, since you cannot buy part of one.
Seam tape and cap fasteners are separate items. A rule of thumb is one roll of seam tape per roll of wrap, plus a bucket of cap nails or staples; this tool sizes the wrap itself.
wall area = 140 ft perimeter × 10 ft = 1,400 sq ft
with laps = 1,400 × 1.10 = 1,540 sq ft
rolls = 1,540 ÷ 900 = 1.7 → round up to 2 rolls