Wallpaper Rolls Calculator Formula
Understand the math behind the wallpaper rolls calculator. Each variable explained with a worked example.
Formulas Used
Gross Wall Area
gross_area = room_perimeter * wall_heightNet Wall Area (after openings)
net_area = room_perimeter * wall_height - openings_areaUsable Coverage per Roll
coverage_per_roll = pattern_repeat > 0 ? roll_length * (roll_width / 12) * 0.80 : roll_length * (roll_width / 12) * 0.90Rolls Needed
rolls_needed = ceil((room_perimeter * wall_height - openings_area) / (pattern_repeat > 0 ? roll_length * (roll_width / 12) * 0.80 : roll_length * (roll_width / 12) * 0.90))Variables
| Variable | Description | Default |
|---|---|---|
room_perimeter | Room Perimeter(feet) | 52 |
wall_height | Wall Height(feet) | 8 |
openings_area | Total Window & Door Area(sq ft) | 40 |
roll_width | Roll Width(inches) | 21 |
roll_length | Roll Length(feet) | 33 |
pattern_repeat | Pattern Repeat(inches) | 0 |
gross_wall_area | Derived value= room_perimeter * wall_height | calculated |
net_wall_area | Derived value= room_perimeter * wall_height - openings_area | calculated |
usable_per_roll | Derived value= roll_length * (roll_width / 12) | calculated |
How It Works
How to Calculate Wallpaper Rolls
Formula
Net Wall Area = (Perimeter x Height) - Openings Area
Usable Coverage per Roll = Roll Length x (Roll Width / 12) x Efficiency
Rolls Needed = ceil(Net Wall Area / Usable Coverage per Roll)
Efficiency is typically 90% for solid or random patterns and 80% for patterns with a repeating motif. The repeat causes waste because each strip must be aligned to the pattern.
Standard Roll Sizes
American single rolls: 21 in wide x 33 ft long (about 57 sq ft gross). European rolls: 21 in wide x 33 ft long. Double rolls are twice the length.
Worked Example
A room with 52 ft perimeter, 8 ft ceilings, 40 sq ft of openings, standard 21-inch rolls at 33 ft, no pattern repeat.
- 01Gross wall area = 52 x 8 = 416 sq ft
- 02Net area = 416 - 40 = 376 sq ft
- 03Coverage per roll = 33 x (21/12) x 0.90 = 51.97 sq ft
- 04Rolls needed = ceil(376 / 51.97) = 8 rolls
Ready to run the numbers?
Open Wallpaper Rolls Calculator