House Wrap Calculator

Use this house wrap calculator to work out how many rolls of housewrap, seam tape, cap fasteners and window flashing tape you need to cover your walls and gable ends. Enter your dimensions and get a conservative, rounded-up shopping list in seconds.

Gable-end elevation. Dashed blue lines are house wrap courses (2 in. horizontal laps); they update when you calculate.

How to Use This House Wrap Calculator

Enter the length and width of your house, the total wall height, and the rise of each gable end. Pick the roll size you plan to buy and set a waste allowance, then press Calculate. You get the number of rolls to buy (always rounded up), seam tape, cap nails or staples, window and door flashing tape, and a side-by-side comparison of every common roll size.

Why This Matters

House wrap is your wall's water-resistive barrier. It sheds bulk water that gets behind siding while letting vapor escape. Running out halfway up a wall is expensive: the crew stands idle, a second trip to the lumberyard eats an hour or two, and exposed OSB or plywood sheathing soaks up rain. Many products only tolerate a few months of UV exposure (commonly 3 to 9, so check your label), so leaving gaps is not a safe plan.

Buying too much is not free either. A 9 ft × 150 ft roll often runs well over $150, and leftovers rarely get used. A typical 1,800 sq ft ranch has around 1,400 to 1,800 sq ft of wall surface including gables. Roll size changes the answer: on 9 ft walls a 9 ft roll wraps the whole height in one pass, while 3 ft rolls need four courses and many more laps. Homeowners planning a DIY re-side, builders pricing a bid, and siding contractors ordering for a crew all need a number they can trust before the truck is loaded.

How It's Calculated

Most installers run house wrap horizontally, starting at the bottom and lapping each upper course over the lower one so water sheds. This calculator follows that method and rounds every result up.

Perimeter P = 2 × (Length + Width) Usable roll width = Roll width − 2 in. Wall courses n = 1 if Height ≤ Roll width else 1 + ceil((Height − Roll width) / usable width) Wall linear ft = n × P Gable linear ft = 2 × sum of each course's widest width Needed ft = (Wall + Gable) × (1 + waste) × L / (L − 0.5 ft) Rolls = ceil(Needed ft / Roll length L)

The 2 in. horizontal lap and 6 in. (0.5 ft) vertical lap follow the water-resistive barrier lap rules in IRC R703.2 (2018 and 2021 editions). Manufacturers often require the same or larger laps, so follow your product's instructions. Gable courses are counted at their widest point, because triangle offcuts are hard to reuse. Openings are not subtracted: wrap goes on continuously and is cut out afterward.

Seam tape is the horizontal seam length plus one vertical seam per roll, plus 10%, in 164 ft rolls. Cap fasteners are estimated at one per 1.33 sq ft (about 16 in. by 12 in.), plus 10%, in boxes of 1,000. Flashing tape is the opening perimeters plus 25% for sill pans and corner overlaps, in 75 ft rolls. Local codes vary, and this tool is an estimating aid, not engineering, permit or inspection approval.

Worked Example

A 40 ft × 28 ft house with 9 ft walls, a 7 ft gable rise, 9 ft × 150 ft rolls, 10% waste, 8 windows (3 × 5 ft) and 2 doors (3 × 6.8 ft):

Perimeter = 2 × (40 + 28) = 136 ft. Walls = 136 × 9 = 1,224 sq ft; gables = 28 × 7 = 196 sq ft; total surface = 1,420 sq ft.
The 9 ft wall fits one 9 ft course, so wall wrap = 136 ft.
The 7 ft rise fits in one course, and each gable needs 28 ft at its widest. Two gables = 56 ft.
Subtotal = 192 ft. Add 10% = 211.2 ft. Allow for vertical laps (×150 ÷ 149.5) = 211.9 ft, or 1,907.2 sq ft of material.
211.9 ÷ 150 = 1.41, rounded up to 2 rolls. (9 × 100 rolls would need 3.)
Seam tape: 56 ft horizontal + 2 × 9 ft vertical = 74 ft, ×1.1 = about 82 ft, so 1 roll.
Cap fasteners: 1,420 ÷ 1.333 = 1,065, ×1.1 = 1,172, so 2 boxes.
Flashing tape: windows 8 × 16 ft = 128 ft, doors 2 × 19.6 ft = 39.2 ft, total 167.2 ft × 1.25 = 209 ft, so 3 rolls of 75 ft.

Tips & Common Mistakes

Don't deduct windows and doors. Cutting out openings leaves offcuts that are rarely usable, and the extra wrap around openings gets folded into the flashing.
Match the roll to your wall height. A 9 ft roll on an 8 ft wall wastes a foot, but it also covers the rim joist, which is often the better use.
Lap shingle-style. The upper course goes over the lower one, at least 2 in. horizontally and 6 in. at vertical joints, so water never runs behind a seam.
Flash openings before the siding. Sill pan first, then jambs, then head, with the wrap lapping over the head flashing. Follow the window maker's sequence.
Add extra for complex houses. Bump the waste slider to 15–20% for dormers, bump-outs, many corners or first-time DIY installs.
Use the right fasteners. Cap nails or cap staples into studs, and check your wrap's maximum spacing. Plain staples tear out in wind.

Frequently Asked Questions

How many square feet does a roll of house wrap cover?

A 9 ft × 150 ft roll is 1,350 sq ft, a 9 ft × 100 ft roll is 900 sq ft, a 10 ft × 100 ft roll is 1,000 sq ft, and a 3 ft × 100 ft roll is 300 sq ft. Real coverage is lower once you subtract the laps and cut waste, so use the calculator rather than the printed number.

Do I subtract windows and doors when estimating house wrap?

No. Wrap is installed continuously over openings and then cut out with an X or modified-I cut and folded into the rough opening. Subtracting openings is how most people end up short.

How much extra house wrap should I buy?

10% is a sensible minimum for a simple rectangular house once laps are counted. Use 15–20% for houses with dormers, many corners or multiple stories, or if you're new to the job.

Do I have to tape house wrap seams?

It depends on the product and the warranty. Many manufacturers require seam tape for their system to count as a sealed drainage plane. Code requires lapped joints, and the manufacturer's installation instructions are part of what an inspector checks, so read yours.

Should house wrap go on horizontally or vertically?

Horizontal is standard, because each upper course laps over the lower one and sheds water naturally. Vertical installation is allowed by some manufacturers but needs specific lap and taping details, so check the instructions first.

Is house wrap the same as a vapor barrier?

No. House wrap is a water-resistive barrier that blocks liquid water but lets water vapor pass through so walls can dry. A vapor retarder slows vapor and goes in a different place, depending on your climate zone and local code.