SqFt Math

Wallpaper calculator

Drops cut to the pattern, wall by wall, into whole rolls — a single feature wall too.

By Rohit GaurLast updated September 19, 2026Report a mistake

Set what your measurements are good to and the quantities below allow for the largest the rooms could be.

The roll's label is in
Roll size

A British or European roll is 10 m by 53 cm. American paper is often priced per single roll but sold as double rolls, which unroll as one continuous length — enter the roll you will actually unroll, and price it the same way.

Pattern match

The label says which. A free match has nothing to line up, like a plain or a stripe; a straight match lines up level across every drop; a half drop steps down by half the pattern on every other drop.

The height of one whole pattern, printed on the label. Leave it at 0 for a paper with no pattern to line up.

Floor to ceiling. The paint, wallpaper and drywall pages share it, and every room uses it unless you give that room its own.

Extra at the ceiling and the skirting for a clean cut: Arthouse's calculator allows 10 cm, State of the Wall 4 inches.

Graham & Brown and Arthouse's calculator allow 10%. Anything above nothing buys at least one whole roll, because a roll bought later can come from a different print batch and not quite match.

What to buy

13 rolls of 20 1/2 in × 33 ft

11 for the walls and 2 spare

Wall area divided by roll area would say 7 rolls. Cut into drops that line up, the walls need 11 rolls: the pattern, and the length left at the end of every roll, are what the area method cannot see.

How the rolls are cut

  1. Walls 8 ft high32 drops of 8.33 ft, 3 from each roll, 8 ft left on each11 rolls
Wall area
384 ft²
Paper on the rolls for the walls
620.13 ft²
Paper that does not end up on the wall
38.1%

Doors and windows are not taken off. The drops beside them still come off whole lengths, and Graham & Brown advise leaving them in for just the right amount of spare.

Rooms

12 ft12 ft

Cutouts (taken off)

Extra areas (added on)

12 × 12 = 144 ft²

Room area: 144 ft²Perimeter: 48 ft

Use the height set above

Walls to paper

Untick the walls you are not papering. One wall on its own is a feature wall.

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Why wall area divided by roll area comes out short

Wallpaper is hung in vertical lengths called drops, each cut from a roll, and every drop has to start at the same point in the pattern as the one beside it. So the real questions are how many drops each wall takes, how long each drop is once it is rounded to the pattern, and how many of them one roll gives. That is how a manufacturer’s own calculator counts — Arthouse’s does exactly this — and it is why the area shortcut runs short as soon as a paper has a pattern.

Here is one 4 × 3 m room with a 2.4 m ceiling, on the standard 10 m × 53 cm roll, allowing 10 cm on every drop for trimming. It needs 28 drops whatever the paper: 8 on each long wall and 6 on each short one.

Paper Each drop Drops per roll Rolls for the walls Wall area ÷ roll area
Plain or free match 2.5 m 4 7 7
50 cm straight match 2.5 m 4 7 7
53 cm straight match 2.65 m 3 10 7
64 cm straight match 2.56 m 3 10 7
50 cm half drop 2.5 m + 25 cm 3 10 7
64 cm half drop 2.56 m + 32 cm 3 10 7

The 50 cm straight match costs nothing extra because 2.5 m happens to be exactly five repeats. A 53 cm repeat does not divide 2.5 m, so every drop is rounded up to five repeats, 2.65 m — and the fourth drop no longer fits on the roll. Three drops a roll instead of four is the difference between 7 rolls and 10, and the area method cannot see it. Each total above then gets a spare roll on top.

Half drops

On a half-drop paper the pattern steps down by half a repeat on every other drop. Cut one drop after another from a roll and each new drop has to skip half a repeat to get back in step. This page follows the rule DecoratorsBest gives: work each drop out like an ordinary repeat and add half a repeat to every drop after the first. Other guides allow more — I Love Wallpaper adds one and a half repeats to every drop — and installers save some of it by cutting alternate drops from two rolls, which the Wallcovering Installers Association describes. So the count here errs on the side of enough.

American rolls

An American single roll holds 34 to 36 square feet and a Euro roll 28 to 30, and in the US both are usually priced by the single roll but sold as double rolls: two single rolls in one continuous strip, as the Wallcovering Installers Association defines it, packaged that way to waste less. Hirshfield’s gives the common roll as 20½ inches by 16½ feet a single roll, so a double roll is one 33 ft length — the roll to enter here, and the one to price.

It matters on an 8 ft wall. With the 4 inches of trim State of the Wall allows, each drop is 8 ft 4 in; four of them need 33 ft 4 in, four inches more than the roll holds. So every double roll gives three drops and leaves 8 ft over. A 12 × 12 ft room with 8 ft walls takes 32 drops and 11 double rolls, where wall area divided by roll area says 7 — and with no trim allowance at all it would be 8. The page shows what each roll leaves over, because those pieces are what cover the wall above a door and under a window.

Hirshfield’s counts rolls by area instead, with a usable yield per single roll that falls as the repeat grows: 25 sq ft for a repeat up to 6 inches, 22 up to 12, 20 up to 18 and 18 up to 23 inches.

Feature walls

Wallpaper often goes on just one wall. Under each room, untick the walls you are not papering: the walls are listed with their lengths, in the order the room’s outline runs. One 4 m wall on the standard roll takes 8 drops — 2 rolls of a plain paper, 3 of a 64 cm half drop — plus the spare.

A curved room is papered as one wall the length of its perimeter. A room drawn by base and height has no measured walls, so it is left out and the page says so; give its sides and its walls appear.

Doors, windows and spare rolls

Doors and windows are not taken off. The drops beside them still come off whole lengths, and Graham & Brown advise leaving them in the measurement for just the right amount of excess.

For spares, Graham & Brown allow an extra 10% and Arthouse’s calculator adds 10% with a minimum of one roll, which is the rule here. Farrow & Ball simply say to add one more roll, because colour and pattern can differ slightly between batches — and the installers’ dictionary says every roll should come from the same dye lot. So buy the spare with the rest, not later.

What this version does not do yet

Where these numbers come from