🧻 Wallpaper Calculator

Enter your room's perimeter and wall height to find how many standard wallpaper rolls you need, including an allowance for pattern matching waste.

Room perimeter (ft)

Wall height (ft)

Roll width (in)

Roll length (ft)

Waste allowance for pattern matching (%)

Two counts, and the larger one wins

Wallpaper is hung in full-height strips, so the area method on its own under-buys. This page works it out both ways and takes whichever is higher. The strip method divides the roll length by the wall height and rounds down, because a part strip is no use; the area method pads the wall area by your waste allowance and divides by the roll's coverage.

strips per roll = floor(roll length / wall height)
strips needed   = ceiling(perimeter / roll width in feet)
rolls (strips)  = ceiling(strips needed / strips per roll)
rolls (area)    = ceiling(wall area x (1 + waste%) / roll area)

The defaults describe a 12 x 10 ft room with 9 ft walls: 44 ft of perimeter, 396 sq ft of wall, rolls 20.5 in wide by 33 ft long. Each roll gives 3 usable strips, not 3.67, and the walls need 26 strips - so 9 rolls. The area method lands on 9 as well.

Why a 56 sq ft roll does not cover 56 sq ft

That roll holds 56.4 sq ft of paper, but three 9 ft strips use only 27 ft of its 33 ft length. Six feet is offcut before anyone has thought about the pattern. That is 18% gone to the arithmetic alone, which is why the strip count is the one that decides.

The pattern repeat costs more on top. With a straight match, every strip after the first may need up to one full repeat of extra length to line up. A 21 in repeat on a 9 ft wall means cutting strips at nearly 11 ft.
A half-drop or random match changes the sum again - drop matches waste the most, plain and random-match papers the least.
15% suits a small repeat. Push to 20-25% for a large repeat, a drop match, or a room with a chimney breast and alcoves where short strips pile up.

Check the batch or dye lot number on every roll before you leave, and buy the whole room in one go. Wallpaper is printed in runs and the colour drifts between them - two rolls from different batches side by side on the same wall is the classic way a good job goes wrong. Note too that rolls are often sold as double rolls but priced as singles, so confirm which unit you are being quoted.

Offcuts are not always wasted. The short pieces left over are the ones that go above a door or under a window, so hang the full-height walls first and keep the tail ends until those gaps are papered.

Frequently asked questions

How many rolls of wallpaper for a 12x10 room?

With 9 ft walls, 9 standard rolls. The room has a 44 ft perimeter, which takes 26 strips at 20.5 in wide, and a 33 ft roll yields only three 9 ft strips.

How many strips do I get from one roll?

Divide the roll length by your wall height and round down. A 33 ft roll gives three 9 ft strips or four 8 ft strips - so an 8 ft ceiling is markedly cheaper to paper than a 9 ft one, for the same wall area.

How much extra should I allow for pattern matching?

15% for a small or random repeat, 20-25% for a large or half-drop repeat. The cost is the length thrown away at the top of each strip to line the pattern up, so it scales with the size of the repeat, not the room.