How the wallpaper estimate works
The tool computes the four-wall area as 2 x (length + width) x height, gives a 20% credit for doors and windows (you still waste paper around frames), then adds a pattern-waste percentage and divides by the usable area of your chosen roll.
Net = wall area x 0.8 (openings credit)
Rolls = (net x (1 + waste%)) / usable area per roll
Pattern repeat is the hidden cost
A "free match" pattern wastes almost nothing beyond normal cuts. A large repeat (18-24 inch) forces every strip to start at the same point, discarding the offcut at top and bottom of each drop. For those, set waste to 20-30% or you will run short and be unable to match a discontinued batch.
Recommended tools & supplies
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Use cases
- Accent wall - enter one wall's width, not the whole room, to avoid overbuying.
- Full bedroom - include the closet and door; the openings credit keeps you honest.
- Ceiling paper - treat ceiling length x width as the wall, with height set to 1 ft equivalent, or just run the room-area tool and paste the number.
- Rental flips - managers standardize a cheap free-match roll across units to minimize waste.
Roll types at a glance
US single rolls are small and now rare for full rooms. US double rolls (about 48 sq ft usable) are the common retail unit. European rolls are wider and longer, covering ~54 usable sq ft. Always read the label for the usable figure, not the gross printed area.