Wallpaper Calculator

How to use this wallpaper calculator

1. Choose “Whole room” to enter one room’s length, width, and wall height. Choose “Single walls” for an accent wall, or for walls of different heights, such as under a sloped ceiling.
2. Measure each wall’s width, and the height where the paper will go. Measuring from floor to ceiling is fine and leaves a little extra.
3. Pick the roll size from the label: a US double roll, a European roll, or another size you enter yourself.
4. Enter the pattern repeat and the match type from the label. Stripes, textures, and grasscloth are usually a free match with nothing to line up.
5. Leave doors and windows in your measurements. If a wall is mostly glass, enter the width of that opening under the settings.

The result gives the number of rolls, the strips you’ll cut, and whether the last roll leaves enough for a spare strip. The cost uses an example price per roll that you can change.

How the calculator works

Dividing your wall area by the area of a roll undercounts, often by a third or more. Wallpaper goes up in full-height strips that can’t be pieced together, and each strip has to start at the right point in the pattern. Whatever is left at the end of a roll that is too short for another strip is waste. So the calculator counts strips:

strips per wall = wall width ÷ roll width, rounded up
strip length    = wall height + 4 in
paper per strip = strip length, rounded up to whole repeats
                  (half drop: up to 1.5, 2.5, 3.5 … repeats)
strips per roll = 1 + (roll length − one repeat − strip length)
                      ÷ paper per strip, rounded down
rolls           = all strips ÷ strips per roll, rounded up

The 4 inches is Graham & Brown’s trimming allowance: cut each strip 4 inches longer than the wall, leaving 2 inches at the top and 2 at the bottom. You can change it in the settings.

When you cut strip after strip from one roll, the next strip can only start where the pattern matches again. On a straight match that’s the next whole repeat, so the paper between the end of one strip and that point is waste. The last strip on a roll needs only its own length. You also lose up to one repeat at the start of each roll while you find the first match, so we take one repeat off the roll length.

A half-drop match shifts every other strip down by half a repeat. Cut in order from one roll, each strip runs to the next point where the pattern sits half a repeat lower, which is 1.5, 2.5, 3.5 repeats and so on. Depending on the wall height, that wastes more or less than a straight match would. Some paperhangers cut the odd strips from one roll and the even strips from another to save paper. Our count assumes the simpler way, so it may leave you a little extra.

Each wall is rounded up on its own. Doors and windows stay in, as Graham & Brown recommends, because the short pieces around them come out of full strips and the pattern still has to match. When walls have different heights, the calculator fits the longest strips onto rolls first and fills the ends with shorter ones.

A worked example

Say you’re papering a 12 × 14 bedroom with 8-foot walls, using US double rolls (20.5 inches by 33 feet) with a 20.5-inch straight repeat.

• The two 12-foot walls: 144 inches ÷ 20.5 = 7.02, so 8 strips each
• The two 14-foot walls: 168 ÷ 20.5 = 8.2, so 9 strips each
• That’s 34 strips in all
• Strip length: 96 + 4 = 100 inches
• Paper per strip: rounded up to five repeats = 102.5 inches
• Each roll: 396 inches − 20.5 = 375.5 inches. Three strips take 2 × 102.5 + 100 = 305 inches, and a fourth would need 407.5, so 3 fit
• Rolls: 34 ÷ 3 = 11.3, so 12 double rolls

The area method would have said 416 square feet ÷ 56 = 7.4, or 8 rolls. Eight rolls give only 24 strips, 10 short of what the room needs. Twelve rolls leave room for 2 spare strips, which is about right for a mistake or a repair later.

Now raise the ceiling to 10 feet. Each strip is 124 inches, and the next can’t start until 143.5 inches, seven repeats in. Three strips would need 20.5 + 2 × 143.5 + 124 = 431.5 inches, more than a roll holds. Only 2 fit, so a 14-foot accent wall goes from 3 rolls to 5. A half drop doesn’t help at that height, since each strip still runs to 133.25 inches.

Strips per double roll

How many strips one US double roll (20.5 inches by 33 feet) gives, with 4 inches for trimming:

When the count drops from 3 to 2, you need 50% more rolls for the same wall. That’s why a tall room with a large repeat can cost far more than the square footage suggests. In the 9 ft 6 in row, the half drop gets only 2 strips while the straight match still gets 3.

Tips for buying and hanging wallpaper

• Check the batch number on every roll before you open any of them. Colors can shift slightly from one printing to the next.
• Order a sample first. It shows the true repeat and color, and how the match works at a seam.
• Start in the least noticeable corner, such as behind a door. The last strip rarely matches the first, so put that seam where nobody looks.
• Prime new or patched drywall before papering. The paper sticks more evenly, and it comes off later without tearing the drywall’s paper face. If you’re still hanging the walls, the drywall calculator works out the sheets and supplies.
• Paint the ceiling and trim first so drips never land on fresh paper. The paint calculator uses the same room size.
• Keep the leftovers rolled up and labeled with the room. A matching strip fixes a torn or stained section in minutes.