Wallpaper calculator
Wallpaper is figured in strips, not square feet. Each strip has to be cut to the wall height plus enough to match the pattern, and a roll yields only so many strips. Enter the walls, the roll you are buying, and the pattern repeat, and the calculator tells you how many rolls to order.
How the wallpaper calculator works
The calculator starts with the total width of wall to cover, divides by the roll width to find how many vertical strips are needed, and then works out how many full strips a roll yields. Each strip is cut to the wall height plus 4 inches for trimming at top and bottom; with a pattern repeat, the strip length is rounded up to the next whole repeat so the pattern lines up across seams, which is where most wallpaper waste comes from.
Doors and windows reduce the count a little, but not by their full area, because the strips above and below an opening still come from a full-height cut. The calculator credits half a strip per door and a quarter strip per window, a conservative rule professional hangers use.
Formula
strip length = (wall height × 12 + 4) rounded up to the pattern repeat
strips per roll = floor(roll length × 12 ÷ strip length)
rolls = ceil((perimeter × 12 ÷ roll width − 0.5 × doors − 0.25 × windows) ÷ strips per roll)
Example: a 14 × 12 ft room with 8 ft walls, one door and two windows, in 20.5 in × 33 ft double rolls with no repeat: 52 ft of wall is 31 strips minus 1 for openings, so 30 strips. Each 100 in strip fits 3 per roll, so 10 double rolls. With a 24 in repeat the strip grows to 120 in, still 3 per roll, so 10 rolls. On 9 ft walls with a 36 in repeat each strip is 144 in, only 2 fit per roll, and the order jumps to 15 rolls.
Buying and hanging tips
- Check whether the price is per single or double roll. Most US paper is priced per single roll but sold only in double-roll bolts.
- Straight match and drop match patterns both need the repeat allowance; a drop match may need half a repeat more per strip, so round up.
- Peel-and-stick rolls are short. Measure strips carefully; there is less slack than with traditional paper.
- Prime bare drywall with a wallpaper primer or sizing. Paper on raw drywall will tear the surface off when it is removed.
- Start in the least visible corner; the last seam will not match the pattern.
Painting the rest of the room? The paint calculator uses the same room dimensions.
Common sizes, already worked out
Common questions
How many rolls of wallpaper do I need for a 12x12 room?
About 10 double rolls of 20.5 in × 33 ft paper for 8 ft walls with a door and two windows and no pattern repeat. A pattern repeat of 24 in or more pushes it to 10 to 14 rolls.
How much wall does a double roll cover?
A 20.5 in × 33 ft double roll is 56 sq ft of paper, but after trimming and pattern matching expect to cover 45 to 50 sq ft of wall, or three 8 ft strips. Taller walls or a big repeat reduce it to two strips.
Do I subtract doors and windows when calculating wallpaper?
Only partially. Subtract about half a strip per standard door and a quarter strip per window, because the pieces above and below openings are cut from full-length strips anyway. Do not subtract their full square footage.
What is pattern repeat on wallpaper?
The vertical distance before the design repeats itself, printed on the label. Each strip must be cut to a multiple of the repeat so the pattern matches at the seams, which means more waste per strip as the repeat gets larger.