Calculate
The Number Of Single Rolls Needed For A Room
Plan Before You Buy
It pays to make a generous estimate of your needs when purchasing wallpaper. If you run short during installation and need to order additional rolls, you may not be able to obtain an exact color match. And if you need to patch damaged areas later, you'll be glad to have matching material on hand.
During each printing, manufacturers use fresh batches of colored ink. Each newly mixed batch of color is identified by a run number printed on the package of each bolt of wallpaper. Check that all your bolts have the same number before you even unroll them.
Choosing the proper adhesive is equally important. Be sure to use the adhesive recommended for the type of covering you're installing.
Figuring Your Wallpaper Needs
To decide how much wallpaper you need, first measure the wall or room with a steel tape. Use a notebook to recorded your figures. You'll want to take the notebook with you later when you're shopping for your wallpaper; this way you can be sure to purchase the amount you need.
Measure the height and width of each wall(including openings);then multiply the two figures to determine the total area of the wall in square feet. Add the square footage of all the walls to be covered to determine the total area.
After you figure a room's total square footage including openings, deduct 15 square feet for every averagesize door or window. For larger or unusually shaped openings, measure the height and width of each opening and deduct the exact square footage from your total.
Allow For Pattern Repeats
If you're using patterned wallpaper, you can't accurately estimate the number of rolls you need until you figure out the number of pattern repeats that will fit your actual wall height. Pattern books provide the repeat height on the back of each pattern page. Note that a drop match pattern requires only half the number of inches as its repeat measurement.
To allow for pattern repeat, divide the height of the wall by the number of inches between the pattern repeat; if you have a fractional remainder, round it off to the next highest number. For example, a 96 inch wall height divided by an 18inch pattern repeat gives you 5.33 repeats, rounded off to 6.
Then, multiply the repeat measurement by the number of repeats you'll need to determine the working height figure you must use. In the case above, multiplying the 18inch pattern repeat by 6 repeats tells you that you must calculate your wallpaper need according to the requirements of the 108inch wall, rather than the actual 96inch wall.
If, as in this case, the actual wall height differs from the height required by your pattern repeat, purchase the additional number of rolls necessary to allow for your pattern repeats.
Borders
You may want to hang a coordinating border around the room at the top of the walls. To determine the amount of border, measure the width of all walls to be covered and divide by three. Since borders are sold by the yard, this will give you the number of yards needed.
If you plan to use the border in any other areas, measure them and add to the yardage accordingly. Include some additional working length for mitering the corners around openings, if neccessary.


 How
Many Rolls?
Once you've calculated and recorded the total square footage of
wall space to be covered( with openings deducted), you'll need to determine
the number of single rolls of wallpaper needed. Though you can estimate
the amount using the chart below, the following instructions will give
you a more accurate count.
Though priced by the single roll, wall covering
is sold in multipleroll bolts. Coverings vary in width from 21 to 36
inches, but they have the same total square footage, depending on whether
they're standard or European rolls. This means that wider rolls are
shorter in length than narrower rolls
A standard single roll contains 36 square feet
of material. The cutting and trimming you'll do will deduct about 6
square feet, so figure on 30 square feet of usable wallpaper from each
roll you buy.
A European single roll contains 29 square feet.
After cutting and trimming, plan on having 25 square feet of usable
material per roll.
To figure the total number of single rolls
you need, divide the total square footage of wall space by 30
(25 for European rolls) square feet. If you're left with a fractional
remainder of square feet, buy an additional roll.
For a quick and generally reliable estimate of the number of rolls of
wallpaper you'll need to cover your room, use the chart below. This
type of chart is found in the front of most sample books.
Estimating Wallpaper
Distance Around Room in
Feet 
Number
of Single Rolls Needed
Height of Ceiling 
Number of Yards for Borders 
Single Rolls for Ceiling 
8 Feet 
9 Feet 
10 Feet 
28 
8 
8 
10 
11 
2 
30 
8 
8 
10 
11 
2 
32 
8 
10 
10 
12 
2 
34 
10 
10 
12 
13 
4 
36 
10 
10 
12 
13 
4 
38 
10 
12 
12 
14 
4 
40 
10 
12 
12 
15 
4 
42 
12 
12 
14 
15 
4 
44 
12 
12 
14 
16 
4 
46 
12 
14 
14 
17 
6 
48 
14 
14 
16 
17 
6 
50 
14 
14 
16 
18 
6 
52 
14 
14 
16 
19 
6 
54 
14 
16 
18 
19 
6 
56 
14 
16 
18 
20 
8 
58 
16 
16 
18 
21 
8 
60 
16 
18 
20 
21 
8 
62 
16 
18 
20 
22 
8 
Choosing The Proper Adhesive
Wallpaper dealers stock adhesives for every type of installation. To find an adhesive suitable for your material. check the manufacturer's instructions or ask your dealer.
Adhesives come in both dry and premixed forms. Dry adhesive is made from a wheat formula; premixed is made from a nonorganic or synthetic formula.
You can use either dry adhesive or the premixed adhesive recommended by the wallpaper manufacturer to apply porous materials such as standard papers and oriental weaves. If you're planning to add a protective coating to a porous wall covering, always use premixed vinyl adhesive, rather than dry adhesive, to prevent mildew.
To install nonporous covering  vinyls, foils, mylars and other specially treated materials use premixed adhesive; its low moisture content makes it mildewresistant. 
Wallpaper pricing can be confusing. While wallpaper books list prices per Single Roll, the wallpaper is manufactured and sold in Double Rolls. (Some papers are also sold in Triple Rolls.)
While this system may seem odd, double and triple rolls provide longer continuous lengths of paper with more useable full lengths.
For example, a single roll with 13.5 running feet of paper would allow you to cut only one 8 or 9 foot strip per roll, whereas 3 full strips could be cut from a double roll (9 yards or 27 feet, long).
So, keep in mind that even though a wallpaper book lists the price of a Single Roll at, say $20, you'll usually be required to purchase the wallpaper by the Double Roll, at a cost of $40 in this example.
Packaging: European, Metric or American Rolls
Wallpaper is also manufactured in a variety of widths. The wider the paper, the fewer strips you'll have to hang and the fewer seams. Here are two common widths:
 European and Metric Double rolls are generally 20.5" wide and contain 56 square feet of paper.
 American Double rolls are wider, at 27" wide and 9 yards long, with about 70 square feet of paper.
 In addition, Wallpaper Borders vary in width but are typically packaged in 5 yard rolls.
Before You Buy Wallpaper
Before ordering wallpaper you'll need to determine if the paper you've selected has a "drop match" or a "straight match", since a drop match means more paper will be needed. An example of a straight match wallpaper would be a plain vertical stripe that doesn't need matching at the seams. Most other patterned wallpapers however are printed with a drop match that ranges from a few inches to a few feet. Drop match papers will require careful matching at the seams.
How do I estimate how much wallpaper will be needed?
Wallpaper comes in double roll bolts. A bolt of wallpaper (5560 sq ft) will contain about 40 to 50 usable sq. ft, depending on the size of the pattern repeat. Most wallpaper comes either 20½" x 33' or 27" x 27' per double roll bolt. There are two popular methods of estimating:
Method #1: Calculate the area of the walls to be covered and divide by the usable sq. ft. per bolt (the usable sq. ft. per bolt estimates can be as low as 40 sq. ft for large repeats of 2024" to as high as 50 sq. ft for small repeats of 12" or random matches); deduct ¼ bolt for each door or window that fully breaks a strip of wallpaper.
Example: To paper an 8' high x 12' long wall with a 20" pattern repeat wallpaper, first calculate the square feet of wall to be covered; 8' x 12' = 96 sq. ft. Allowing 40 sq. ft. per bolt, you would need 96 sq. ft. /40 usable sq. ft per bolt = 2.4 bolts, or, rounding up, three bolts of wallpaper.
Method #2: Calculate the number and length of strips needed (allowing for pattern repeats); then figure how many bolts would be required to yield the strips needed.
Example: To paper an 8' high x 12' long wall with a 20" pattern repeat wallpaper, first calculate the number of strips needed to cover the wall. If the wallpaper comes in 20½" x 33' bolts, it would take eight strips of wallpaper 20½" wide to cover a 144" wall (12'). Next figure how many bolts would be required to yield eight strips. Each strip would have to be five pattern repeats (100") to cover the 8' high (96") wall. Since each bolt is 33' (396") long, each bolt would yield three 100" long strips. To get eight strips, then, would require three bolts of wallpaper.
