Wallpaper Calculator

How to use the wallpaper calculator

Measure the room length, width and wall height in feet, then count doors and full-size windows. The calculator works out your wall area with the same takeoff deductions a painter uses — 21 square feet per door, 15 per window — and then converts that area to rolls using a realistic usable yield rather than the gross square footage printed on the label.

Those two numbers are never the same. A York Wallcoverings double roll measures 20.5 inches by 33 feet, which is 56.4 square feet of paper on the bolt, but no wall ever receives all of it: the last piece of every roll is shorter than a full wall drop, and the top and bottom of each strip gets trimmed at the ceiling line and the baseboard. Plan on the usable figure and the roll count comes out right.

Pattern repeat is the setting newcomers skip and the one that actually decides the order. Graham and Brown defines it as the vertical distance between one point in the design and where that identical point appears again, and lists repeats from 1 to 25 inches across its range.

The geometry is unforgiving: every strip has to be cut to a whole number of repeats so it lines up with its neighbour, so an 8 ft wall and an 18-inch repeat means cutting each strip at 108 inches, not 96, and throwing away the extra foot. That single change takes a 33 ft roll from four full strips down to three.

Farrow and Ball says the same thing from the other side, quoting four drops per roll for striped papers on a 2.4 m wall, three for small repeats, and only two for large ones.

Match type matters as much as repeat size. Graham and Brown distinguishes a straight match, where the design begins and ends within the width of the roll, from an offset match, which has to line up horizontally and vertically at once and, in its own words, requires more wallpaper and creates more waste.

A half-drop is the common offset case: alternate strips start half a repeat down, so consecutive drops come off the roll at staggered starting points and the offcuts get longer. When a product page says half-drop or offset, pick the over-12-inch tier in this calculator even if the printed repeat is smaller, because the tier is standing in for waste, not for the repeat measurement itself.

US wallpaper has a pricing quirk worth understanding before checkout. York Wallcoverings explains that the single roll is the unit of pricing while the double roll is the unit of sale — one physical bolt containing two singles — a leftover of old packaging conventions. This calculator counts double rolls by default because that is what arrives at your door, so when you compare prices, double the per-single-roll figure to get the real cost of a bolt.

European papers are sold differently again: Farrow and Ball rolls are 10 m by 53 cm, about 5.3 square metres or 57 square feet, which makes one European roll almost exactly the size of one US double roll. Buy the whole job in one order, verify the batch numbers match, and keep the leftovers labelled.

What the pattern repeat costs in rolls

The strip arithmetic behind that is worth doing once yourself. A US double roll is 33 feet, or 396 inches. An 8 ft wall needs 96-inch drops, and 396 ÷ 96 = 4.125, so four full strips come off the roll with 12 inches of scrap.

Put an 18-inch repeat on the same paper and every strip has to be cut at 108 inches instead, because 96 is not a whole number of repeats; 396 ÷ 108 = 3.67, so three strips, and the roll that covered 54.7 square feet now covers 41. Farrow and Ball publishes the equivalent figures for its 10 m European rolls on a 2.4 m wall: four drops for stripes, three for small repeats, two for large ones.

The formula, worked line by line

The area half of this calculation is identical to paint: the perimeter of the room times the wall height, less the standard deductions for doors and windows. What makes wallpaper different is the divisor.

Paint divides by a coverage rate that describes how far a liquid spreads, whereas wallpaper divides by how much of a fixed rectangle of printed paper actually ends up stuck to the wall — and that fraction is set by the pattern long before you pick up a knife.

A roll is not a coverage rate, it is a length. You cut whole strips from it, and any part of the roll shorter than one full wall drop is scrap no matter how much paper it holds.

That is why the usable yield falls in steps rather than smoothly: 25 square feet per single roll on a random match, 22 with a repeat up to 12 inches, 18 once the repeat passes 12 inches. The steps are the strips you lose, not a safety margin someone added.

wall area = 2 × (length + width) × height − (doors × 21) − (windows × 15)
usable yield per single roll = 25 sq ft (no repeat) · 22 (≤12 in) · 18 (>12 in)
double-roll yield = single-roll yield × 2
rolls = wall area ÷ yield, rounded UP to a whole roll

Two things the arithmetic cannot see. Wallpaper is printed in production runs, and Farrow and Ball warns outright that its pattern and colour can differ slightly between batches — invisible in your hand, obvious as a vertical line where two batches meet on a wall, which is why the whole job goes in one order and the batch numbers get checked on arrival.

And this is a shopping estimate, not a hanger’s takeoff: a professional measures wall by wall, plans where the pattern lands at the focal point, and treats an alcove or a chimney breast as its own set of drops. Farrow and Ball’s advice applies to any estimate, including this one — add a roll.

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