Free online wallpaper calculator

How to use

1. Enter the room length, width, and wall height in feet.
2. Set the roll width (inches) and roll length (feet) from your wallpaper label.
3. Enter the number of doors and windows.
4. If the wallpaper has a pattern, enter the repeat in inches — otherwise leave it at 0.
5. Read off the rolls needed, net wall area, and pattern waste.

Formulas

perimeter       = 2 × (room length + room width)
total wall area = perimeter × wall height
net wall area   = total wall area − (doors × 21 ft²) − (windows × 12 ft²)

effective roll length = floor(roll length / pattern repeat) × pattern repeat
                        (if pattern repeat = 0, use full roll length)

roll area       = (roll width / 12) × effective roll length
rolls needed    = ceil(net wall area / roll area) + 1

Worked example

Room 12 ft × 10 ft, 8 ft ceiling, 27-inch × 27-ft rolls, 1 door, 2 windows, no pattern:

perimeter       = 2 × (12 + 10)  = 44 ft
total wall area = 44 × 8          = 352 ft²
openings        = 1×21 + 2×12     = 45 ft²
net wall area   = 352 − 45        = 307 ft²
roll area       = (27/12) × 27    = 60.75 ft²
rolls needed    = ceil(307/60.75) + 1 = 6 + 1 = 7 rolls

Notes

• Always buy all rolls from the same dye lot — colors can vary between lots.
• Heavily textured walls may need extra adhesive and a thicker lining paper underneath.
• Strippable and paste-the-wall wallpapers are easiest for DIY; traditional paste-the-paper types require more skill to align before hanging.