Wallpaper Calculator
The cut-drop model uses actual roll width and length. Room mode rounds each of four walls separately at corners. Each full-height drop includes trim and is rounded to a straight pattern repeat; waste is added to drop count before rounding rolls.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
The cut-drop model uses actual roll width and length. Room mode rounds each of four walls separately at corners.
Worked example
calculated with the default values below
Total wall width 40 ft · Wall height 9 ft · Roll length 33 ft · Roll width 1.75 ft · Pattern repeat 12 in · Doors and windows to deduct 60 sq ft · Extra for mistakes 10 % · Single wall or rectangular room Single wall · Cut-drop model or area estimate Full cut drops · Room length 14 ft · Room width 12 ft · Extra trim per drop (in) 0 · Usable coverage per roll 45 sq ft Rolls to buy 9 · Wall area 360.0 sq ft · Area to cover 300.0 sq ft · Drops needed 23 · Usable length per roll 27.00 ft · Repeat waste multiplier 1.00 x · Total paper length 297.0 ft · Usable full drops per roll 3 · Wall perimeter 40.0 ft
Method and assumptions
The cut-drop model uses actual roll width and length. Room mode rounds each of four walls separately at corners. Each full-height drop includes trim and is rounded to a straight pattern repeat; waste is added to drop count before rounding rolls. Openings affect reported net area but do not remove full drops. A roll too short for one drop is invalid. Area mode is explicitly a coverage estimate and does not simulate pattern matching; the old arbitrary repeat penalty is removed.
General background references
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
drop length = repeat × ceil((height + trim)/repeat); cuts/roll = floor(roll length/drop length); rolls = ceil(ceil(drops × (1 + waste/100))/cuts per roll); area mode = ceil(net area × (1 + waste/100)/coverage)
A roll too short for one drop is invalid. Area mode is explicitly a coverage estimate and does not simulate pattern matching; the old arbitrary repeat penalty is removed.
Frequently asked questions
Do doors and windows reduce the roll count?
The cut-drop model uses actual roll width and length. Room mode rounds each of four walls separately at corners. Each full-height drop includes trim and is rounded to a straight pattern repeat; waste is added to drop count before rounding rolls. Openings affect reported net area but do not remove full drops. A roll too short for one drop is invalid. Area mode is explicitly a coverage estimate and does not simulate pattern matching; the old arbitrary repeat penalty is removed.