Wallpaper Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 10/10/2026
The number of rolls is calculated by dividing the wall perimeter into vertical strips (drops) the width of a roll (0.53 m), then working out how many of these strips fit into a roll (10.05 m long). For a room with a 20 m perimeter under a 2.50 m ceiling, you need 11 rolls with a 10% margin.
Explanation
Unlike a simple division of surface areas (wall area ÷ roll area), this calculator uses the drop method, closer to how wallpaper is actually hung: the wall is covered with vertical strips cut to the exact ceiling height, and a 10.05 m long roll (the standard European roll length) almost never divides exactly by this height, leaving an unusable offcut at the bottom of each roll. For example, under a 2.50 m ceiling, a 10.05 m roll yields only 4 full strips (4 × 2.50 = 10 m), not 4.02 as a simple division would suggest — the remaining 5 cm are wasted. The calculator therefore first determines the total number of strips needed to go around the room (perimeter ÷ roll width, 0.53 m), then how many full rolls are needed to produce that number of strips, with an extra margin for cutting around openings and pattern matching. Once the wallpaper is hung, our paint quantity calculator follows the same area-based calculation logic for any walls left painted.
Example: a room with a 20 m perimeter, 2.50 m ceiling
Inputs
Wall perimeter: 20 m. Height: 2.50 m. Margin: 10%.
Calculation
Strips needed = ceiling(20 ÷ 0.53) = 38. Strips per roll = floor(10.05 ÷ 2.50) = 4. Rolls = ceiling((38 ÷ 4) × 1.10) = ceiling(10.45) = 11.
Result
You need 11 rolls for this room.
Frequently asked questions
Why not simply divide the wall area by a roll's area?
Because this approach overestimates a roll's actual coverage: it assumes the roll can be cut with no waste at all, which almost never happens in practice. The drop method accounts for the inevitable offcut when the roll length (10.05 m) doesn't divide exactly by the wall height, giving a more reliable estimate, usually slightly higher.
Should I subtract the area of doors and windows?
This calculator deliberately does not: it counts the total wall perimeter, doors and windows included, which adds a safety margin for the cutoffs around these openings, partly reusable but not always in the right pattern direction. For a room with large openings, you can slightly reduce the perimeter entered if you're confident you'll reuse the offcuts well.
What margin should I plan for a patterned wallpaper?
10% is usually enough for a plain wallpaper or one with a discreet, non-matching pattern. For wallpaper with significant pattern matching (large-scale floral or geometric patterns, in particular), it's better to plan for 15 to 20% margin, since each strip must be positioned to align the pattern with the previous one, which increases material waste.