Enter your room size, roll dimensions and pattern repeat to see exactly how many rolls to order — strip by strip, not just a rough area guess.
Calculated on your device. Nothing is uploaded to a server.
Wallpaper math is genuinely fiddly: rolls have to be cut into strips, strips have to line up with the pattern repeat, and a few inches of waste per strip can quietly cost you an entire extra roll. This tool works the problem the way an installer would — strip by strip — instead of just dividing area by roll size.
Counts exactly how many usable strips come from each roll, not just a rough square-footage ratio.
Every strip is lengthened for the repeat and a trim allowance, so waste is built in from the start.
Start from a US or European preset, or type in the exact dimensions on your roll's label.
Each vertical strip of wallpaper has to reach from floor to ceiling (your wall height) plus a small trim allowance for squaring off the top and bottom, plus the pattern repeat so consecutive strips line up. The calculator adds those together to get one strip's length, then divides your roll's length by that to see how many full strips come out of a single roll — always rounding down, since a partial strip isn't usable. Separately, it divides your room's perimeter by the roll's width to see how many strips the room needs in total, always rounding up. Dividing strips needed by strips per roll, rounded up again, gives the number of rolls to buy. As a sanity check: a 40 ft perimeter room with an 8 ft ceiling, using a standard 27 in by 27 ft US double roll with no pattern repeat, needs 18 strips at 3 strips per roll — 6 rolls. Door and window openings are converted from an area (like the default 21 sq ft door) into an equivalent width at your wall height, then subtracted from the perimeter before the strip count is calculated, since you generally don't paper over them.
The tool works out how many vertical strips fit around your room (perimeter ÷ roll width), how many usable strips come out of one roll (roll length ÷ strip length), and then divides strips needed by strips per roll, rounding up at every step.
A pattern repeat is the vertical distance before a wallpaper's design repeats. Each strip has to be cut long enough to line up with the next one, so a larger repeat adds waste and reduces how many strips you get from a roll.
Imperial uses the common US double roll (27 in wide by 27 ft long). Metric uses the standard European roll (53 cm wide by 10 m long). Both are just starting points — edit them to match the roll you're actually buying.
Yes, for a tighter estimate. The calculator converts each opening's area into an equivalent width at your wall height and subtracts that from the total perimeter before working out strips needed.
A trim allowance is added to every strip length by default to cover top and bottom trimming, and all roll counts round up rather than down. Many installers still buy one extra roll for a large or heavily patterned room.
More free calculators from My Panda Toolbox.