House Wrap Calculator
A house wrap calculator divides wall area by 900 sq ft per roll: 1,800 sq ft of walls needs 2 rolls, or 3 rolls once you add 10% for overlaps and waste.
House wrap calculator formula
A house wrap calculator divides the area of the walls by the area one roll covers, then rounds up to a whole roll. Rolls = wall area ÷ 900, rounded up. The 900 comes from a 9 ft wide, 100 ft long roll. A checkbox adds 10 percent for overlaps and waste before the rounding.
The formula in plain words
Find the wall area in square feet. Divide it by 900 to see how many rolls that is. Round up, because you cannot buy a part of a roll. If you tick the waste box, multiply the area by 1.1 first.
Worked examples
These match the calculator exactly.
- One long wall as a spot check: 40 ft × 10 ft = 400 sq ft
- Rolls: 400 ÷ 900 = 0.44, rounded up to 1 roll
- With 10% extra: 440 sq ft, 0.49 rolls, still 1 roll
- Cost at $150 per roll: $150
- A small house: 1,800 sq ft of walls
- Rolls: 1,800 ÷ 900 = 2.0, which is 2 rolls
- With 10% extra: 1,980 sq ft ÷ 900 = 2.2, rounded up to 3 rolls
- Cost at $150 per roll: $300 without extra, $450 with it
The jump from 2 rolls to 3 shows why the waste allowance matters when a number sits exactly on a roll.
Common house wrap rolls
| Roll size | Coverage | Notes |
|---|---|---|
| 9 ft × 100 ft | 900 sq ft | Size the calculator uses |
| 9 ft × 150 ft | 1,350 sq ft | Fewer seams on big walls |
| 10 ft × 100 ft | 1,000 sq ft | Fits taller first floors |
Brands and local stores differ, so roll sizes change. Check the label of the roll you plan to buy. If the coverage differs from 900 sq ft, divide your wall area by that figure by hand.
How to measure wall area
Measure the perimeter of the house along the ground. Multiply it by the wall height from the foundation to the top plate. A house that is 40 ft by 30 ft has a perimeter of 140 ft. At 9 ft high that is 1,260 sq ft for one story.
For a second story, add the second floor height too. Gable ends are triangles: base times height divided by 2. Add them to the total. A tall gable can add 100 sq ft or more.
You can also use the tool as a rectangle. Enter the perimeter as the length and the wall height as the width.
Installing the wrap
Start at a bottom corner and work upward so that each upper sheet laps over the one below. Lap vertical seams by the amount the manufacturer asks for, and tape them with the recommended tape. Flash around windows and doors as the instructions show. Fasten with cap nails or staples approved for your product.
Leave the wrap exposed for no longer than the manufacturer allows. Sunlight can degrade it before the siding goes on. Use the wrap your siding maker accepts.
Cost and what drives it
The calculator multiplies the whole rolls by a price per roll, with $150 as a starting figure. Price depends on the brand, the roll size and the store, so replace it with a quote. Tape, cap nails and flashing are extra. A rough way to compare is to divide the roll price by 900 to get a cost per square foot, then compare rolls of different sizes on that basis.
Seams and laps
Manufacturers give a minimum lap for horizontal and vertical seams, often several inches, and they print guide lines on the sheet. Those laps use up a share of every roll, which is why the 10 percent box exists. A house with many windows, bump-outs and gables eats more wrap in cuts than a plain box. If your walls are broken up, use 15 percent and keep the leftover for repairs.
Common mistakes
- Forgetting gables. They are easy to skip and can take an extra roll.
- Not rounding up. Part of a roll is not for sale.
- Using the old foundation footprint. Include bump-outs and porches that are walled in.
- Cutting too short at corners. Wrap that stops at a corner leaves a gap, so extend it around.
Related pages
Once the wrap is up, plan the siding with the vinyl siding calculator and price it with the vinyl siding cost calculator. If you want stone on the lower wall, see the stone veneer calculator.
Frequently asked questions
How many rolls of house wrap do I need?
Divide the wall area in square feet by 900, since a 9 ft × 100 ft roll covers 900 sq ft, then round up. 1,800 sq ft is exactly 2 rolls. With the 10 percent allowance it is 1,980 sq ft, which rounds up to 3 rolls.
How much does a roll of house wrap cover?
The calculator assumes a 9 ft wide by 100 ft long roll, which is 900 sq ft. Some brands sell 10 ft wide rolls or 150 ft long rolls, so enter your own coverage when you shop.
Should I add extra for overlaps?
Yes. Manufacturers call for overlapping seams, and the wrap runs past window and door openings and around corners. Tick the 10 percent box, or go a little higher on a house with lots of gables and corners.
Do I count window and door openings?
Counting them gives a slightly generous order, which usually covers the overlaps and cutting waste. If you subtract large openings, keep the 10 percent allowance so you do not run short.
Where does the wrap go?
It goes over the sheathing and under the siding, with seams lapped so water sheds downward like shingles. Follow the manufacturer's instructions for taping, flashing and fasteners.
Estimates only. Verify quantities with your supplier before purchasing.