Wallpaper Calculator

Calculate how many rolls of wallpaper you need for a room from the wall height, perimeter, roll size and pattern repeat, with strips per roll and strips needed.

By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.

Quick answer: To estimate wallpaper, divide the room perimeter in inches by the roll width for the number of strips, divide the roll length by the wall height plus 4 in of trim for strips per roll, then divide strips by strips per roll. A 12 x 10 ft room with 8 ft walls, 1 door and 2 windows needs 24 strips of 20.5 in paper, which is 8 rolls of 33 ft.

Your measurements

One wall: area is wall length times height, minus each door and window.

Room lengthftRoom widthftWall heightftFloor to ceiling at the tallest point in the room, since ceilings are rarely level. Or the height of the area you are papering.DoorsEach standard door saves about one strip of 20.5 in paper. Count a double door as two.WindowsEach window saves about half a strip. Do not count windows if the repeat is over 24 in; the pieces above and below rarely match.Roll widthThe net width printed on the label. Most US and European papers are 20.5 or 21 in; 27 in is mostly older American and commercial vinyl.Roll lengthft33 ft is the usual double roll for 20.5 and 21 in paper; a single roll is 16.5 ft and a 27 in double roll is 27 ft. Check the label.Pattern repeatinThe vertical repeat printed on the label. Enter 0 for a plain, textured or random-match paper. For a half-drop match enter the full repeat, not half.

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Rolls to buy8 rollsAll results

Results

Rolls to buy: 8 rolls; 24 strips at 3 strips per roll
Strips needed: 24 strips; 26 strips of 20.5 in around the 44 ft perimeter, minus 2 for doors and windows
Strips per roll: 3; Each strip is 100 in long, including 4 in for trimming
Wall area: 302 sq ft; 8 rolls hold 451 sq ft before trimming and pattern matching

Wallpaper formula

Strips needed = Perimeter (in) / roll width, rounded up, minus 1 per door and 0.5 per window
Strip length (in) = Wall height x 12 + 4, rounded up to a whole pattern repeat
Strips per roll = Roll length (in) / Strip length, rounded down
Rolls = Strips needed / Strips per roll, rounded up

Worked example

A 14 x 12 ft bedroom with 9 ft walls, 2 doors, 2 windows and a 21 in wide, 33 ft roll with an 18 in repeat: the perimeter is 52 ft = 624 in. 624 / 21 = 29.7, so 30 strips, minus 2 for the doors and 1 for the two windows = 27 strips.

Strip length: 9 x 12 + 4 = 112 in, rounded up to whole 18 in repeats = 126 in. 33 ft = 396 in, and 396 / 126 = 3.1, so 3 strips per roll. 27 / 3 = 9 rolls.

Quick reference

Wallpaper for rooms with 8 ft walls (20.5 in x 33 ft rolls, no repeat, 1 door and 2 windows)
Room size	Perimeter	Strips	Rolls
10 x 10 ft	40 ft	22	8
10 x 12 ft	44 ft	24	8
12 x 12 ft	48 ft	27	9
12 x 14 ft	52 ft	29	10
14 x 16 ft	60 ft	34	12
15 x 20 ft	70 ft	39	13

How to calculate wallpaper

Wallpaper is hung in vertical strips, so count strips rather than square feet. Measure the room perimeter in inches and divide by the roll width to get the number of strips around the room. Each strip must be the wall height plus about 4 inches for trimming. If the paper has a pattern repeat, each strip is cut to a whole number of repeats so the pattern lines up from strip to strip.

Divide the roll length by the strip length and round down for the strips you get per roll. With 8 foot walls and a 33 foot roll you get 3 full strips, and the 8 feet left over is only useful above doors and windows. Divide the strips needed by the strips per roll and round up to whole rolls.

Roll sizes, repeats and ordering

Almost all wallpaper now sold in the United States comes as a double roll, 20.5 or 21 inches wide by 33 feet long. The price is often still quoted per single roll. Wide American papers are 27 inches by 27 feet. Read the label for the exact width, length and pattern repeat before you calculate. A 27 inch roll needs fewer strips around the room, but its 27 foot length yields only 2 strips on 9 foot walls.

A half-drop match shifts every other strip by half a repeat and wastes more than a straight match; enter the full repeat. Order every roll at once from one run number, printed on the label by the pattern number, because a second run shifts color at the seam. Buy one extra and return it unopened. Deduct a strip per door and half a strip per window; do not deduct small windows if the paper has a large repeat.

What this calculator leaves out

Wallcovering primer (Roman PRO-999 Rx-35 or Zinsser Shieldz, about 400 sq ft per gallon) over bare drywall, patches and flat paint. Paste for unpasted paper, about 4 double rolls per gallon. Prepasted paper needs a water tray or activator and 5 to 10 minutes of booking; non-woven paste-the-wall papers need neither. Seams are butted, never overlapped. Plan the kill point, where the last strip will not match, behind the entry door. A fresh blade per strip, a 4 ft level and removal of the old paper are extra.

Mistakes that cost money

Buying by square feet: 70 to 80% of a roll reaches the wall; a big repeat on tall walls cuts a roll to 2 strips.
Two run numbers on one wall: the color shifts at the seam; order every roll from one run and buy one extra, returning it unopened.
Hanging on bare drywall: the paper cannot be slid to match and tears the drywall face off on removal; prime with a wallcovering primer first.
Starting off a door casing instead of a plumb line: the pattern leans by the far corner; plumb the first strip after every corner.
Skipping booking time on prepasted paper: it keeps expanding on the wall and seams open by morning; book 5 to 10 minutes per the label.
Wrapping a strip around an inside corner: corners are never plumb, so it wrinkles; wrap 1/8 to 1/4 in and start a new plumb strip.

Key facts

The most common roll today is 20.5 or 21 in wide by 33 ft long (52 cm x 10 m), sold as a double roll covering about 56 sq ft.
A wide American double roll is 27 in x 27 ft, about 60 sq ft; the single roll is 27 in x 13.5 ft.
After trimming and pattern matching, only about 70 to 80% of a roll ends up on the wall.
Allow 4 in extra per strip, 2 in at the top and 2 in at the bottom, for trimming.
Rolls with a large pattern repeat can waste 20 to 25% more paper than a plain or random-match design.

Frequently asked questions

How many rolls of wallpaper do I need for a 12x12 room?

With 8 foot walls, one door and two windows, the room needs 27 strips of 20.5 inch paper. At 3 strips per 33 foot roll that is 9 rolls.

How many square feet does a roll of wallpaper cover?

A 20.5 in x 33 ft double roll holds about 56 square feet, but after trimming and matching you can count on about 42 square feet on the wall. A 27 in x 27 ft American double roll holds 60 square feet.

What is a pattern repeat and how does it change the amount?

The repeat is the vertical distance before the design starts over. Each strip is cut to a whole number of repeats so adjacent strips line up. That lengthens each strip and can reduce the strips per roll from 3 to 2 on tall walls.

Do I need to prime the walls before hanging wallpaper?

Yes. Roll on a wallcovering primer such as Roman PRO-999 Rx-35 or Zinsser Shieldz over bare drywall, patches and flat paint, and over glossy paint after scuff sanding. It seals the surface so the paper can be slid into position and seams stay tight as the paste dries. It also lets the paper strip off later without tearing the drywall face.

Sources and references

How to estimate wallcovering rolls for a room (Wallcoverings Association)
Wallpaper specifications: roll widths, lengths, coverage and pattern match (Brewster Home Fashions)
How to measure and cut wallpaper strips (Brewster Home Fashions)

Next steps for this project

The usual order for a paint & walls project. See all paint & walls calculators.

Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.