How many wallpaper rolls do I need?

Count wallpaper rolls from the actual roll dimensions, room perimeter, wall height, vertical repeat, and trimming allowance.

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ToolWallpaper Calculator
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How it works

Perimeter divided by roll width rounds up to vertical drops, and patterned drops round up to a complete vertical repeat. Only whole adjusted drops fit into one roll; dividing all drops by that count, applying the selected allowance, and rounding up gives rolls.

Formula
drops per roll = floor(roll length ÷ repeat-adjusted drop length)
  • Sanderson’s own calculator asks for roll width, roll length, match type, repeat, and wall dimensions because wide-width papers differ.
  • Only vertical repeat defaults to zero for plain or random-match paper; every product dimension and trimming allowance is explicit.

Worked example

A 4m by 3m room, plain paper
Standard roll, no pattern repeat
Input
											Length m: 4
Width m: 3
Height m: 2.4
Roll length m: 10.05
Roll width m: 0.53
Waste percent: 15
Output
												Wall width total m: 14
Drops: 27
Drop length m: 2.4
Drops per roll: 4
Rolls needed: 8

When to use this

Plain paper maximises wall-height drops, straight-match designs cut to full repeats, and wide-width designer rolls use their own printed width and length.

Edge cases

  • A repeat-adjusted drop longer than the purchased roll is rejected because the roll cannot supply even one unbroken wall-height strip.
  • A leftover shorter than the next complete drop cannot be carried into another roll, so drops per roll always rounds downward.
  • Half-drop matching alternates motif position and is not modelled by vertical-repeat rounding alone; use the manufacturer’s product calculator or a decorator.

References