How the wallpaper roll calculator works
Drops, not square feet
Wallpaper is consumed in vertical drops cut to wall height — never in area. Drops = perimeter ÷ roll width (60 ft ÷ 2.25 ft = 27 drops). Each drop must come from one continuous piece of roll: this is why a room that "is" 480 sq ft does not divide by roll area. The calculator works in drops throughout.
Cuts per roll
Cuts per roll = roll length ÷ (wall height + repeat allowance + trim). A 13.5 ft US roll on an 8 ft wall yields one drop with generous left-over, two drops on low walls. Rolls = ceil(drops ÷ cuts per roll) — then the margin rounds up again, because dye lots.
The margin is not padding
The 10–15% default margin covers pattern miscuts, wall surprises (bulges, patches that eat paste), and future repairs — and because wallpaper is manufactured in batches, next year's replacement roll will not match this year's dye lot. Buying margin is buying the ability to fix a torn panel in 2031.
Doors and windows
Subtract nothing for standard openings unless they are huge: drops still span above and beside doors, and offcuts from openings rarely align with usable drop positions. The calculator measures wall runs, not floor area — enter the perimeter of papered wall.