How to use the wallpaper calculator
Wallpaper is sold by the roll, but it goes on the wall in strips, and a roll can only be cut into whole strips. That is why this wallpaper calculator counts strips first and rolls second, the same way a paperhanger does, and shows the quick square-footage estimate next to it so you can see the difference. All of the math happens in your browser.
- Choose what you are papering. Under Measure, pick Whole room (length, width and wall height), Wall by wall (any number of separate walls), or Accent wall (one feature wall). For a whole room you can also tick Also paper the ceiling.
- Count the doors and windows. Enter how many there are and their size once, under Door and window size. Every length field has its own unit, and you can type
8' 6",96 inor245 cm. - Pick the roll and the pattern. Choose a common roll size or enter the width and length from the label. Then set the pattern match (none, straight or half-drop) and the vertical repeat printed on the label.
- Read the rolls to buy. The results show the rolls, the number of full-height strips and short pieces, how long to cut each strip, how many strips one roll gives, the area method for comparison, the paper left over and, if you enter a price per roll, the cost. Copy the results, download them as a CSV file or print them.
Switch Units to Metric to see areas in square meters and to start new walls in meters. The calculator remembers your last entries on this device.
How to measure a room for wallpaper
Use a tape measure and write every figure down before you buy anything. Measure in the units you are comfortable with; the calculator converts them.
- Wall widths. Measure each wall along the floor, corner to corner, and round up to the next inch or centimeter. For a rectangular room, the length and width are enough, because opposite walls match. For an L-shaped or odd-shaped room, use Wall by wall, or work out the floor plan with the square footage calculator first.
- Wall height. Measure from the top of the baseboard to the ceiling, or to the bottom of any crown molding, in a few places. Older houses are rarely level, so use the largest figure.
- Doors and windows. Measure each opening with its trim. For windows, also measure the height from the floor to the bottom of the trim, because the wall below a window still needs paper.
- The roll label. Write down the roll width and length, the pattern repeat and the match type before you start. They change the answer more than anything else.
If you are stripping old paper first, be careful with what is underneath. The U.S. Environmental Protection Agency warns: "If your home was built before 1978, it is more likely to have lead-based paint." Read the EPA's guidance on sources of lead before you scrape or sand old walls.
How to calculate how many rolls of wallpaper you need
The strip method takes five steps. The calculator does them for every wall, and adds the short pieces above doors and above and below windows:
strips = wall width ÷ roll width, rounded up
cut length = wall height + trim, matched to the pattern
strips per roll = roll length ÷ cut length, rounded down
rolls = strips ÷ strips per roll, rounded up- Measure the walls. Measure the width of each wall and the height from the baseboard to the ceiling. For a room, add the widths to get the perimeter.
- Count the strips. Divide the total width by the width of the roll and round up. Each strip covers one roll width from top to bottom.
- Work out the cut length. Add a trimming allowance, often 2 inches at the top and 2 inches at the bottom, to the wall height. With a patterned paper, round that up so each strip starts at the right point in the pattern.
- Find the strips per roll. Divide the roll length by the cut length and round down. The rest of the roll is an offcut, good only for short pieces.
- Divide and round up. Divide the number of strips by the strips per roll and round up to a whole roll. Buy every roll from the same batch.
Example: a 12 × 12 ft room with 8 ft walls, one 36 × 80 in door and two 36 × 48 in windows set 36 in above the floor, papered with US double rolls (20.5 in wide, 33 ft long) and no pattern to match. The perimeter is 48 ft, or 576 in; 576 ÷ 20.5 is about 28.1, so it takes 29 strips. Each opening covers one whole strip, which leaves 26 full-height strips and 5 short pieces. With 4 in of trim, each strip is cut 8 ft 4 in (100 in), and a 396 in roll gives 3 of them. The full strips need 9 double rolls, and the short pieces come out of the offcuts. That is the example the calculator opens with.
Strip method vs. area method
Many quick estimates divide the wall area by the area of one roll. For the example room that is 4 walls × 12 ft × 8 ft = 384 sq ft, minus 44 sq ft of openings, which leaves 340 sq ft. A double roll holds 56.38 sq ft, so the area method says 7 rolls, two fewer than the 9 the strip count needs.
The difference is the offcut. A 33 ft roll is 396 in long. Three 100 in strips use 300 in, and the remaining 96 in is too short for a fourth strip, so almost a quarter of every roll is left for short pieces or thrown away. The area method treats that offcut as if it could cover wall, which it can't. That is why the calculator leads with the strip count and shows the area method only for comparison.
Small changes move the answer a lot. With a 2 in trim allowance instead of 4 in, each strip is cut 98 in, a roll gives 4 strips, and the same room needs 7 rolls. Ask whoever is hanging the paper what allowance they use, and set it in the calculator.
| Wall height | Cut length | Strips per roll |
|---|---|---|
| 8 ft | 8 ft 4 in | 3 |
| 9 ft | 9 ft 4 in | 3 |
| 10 ft | 10 ft 4 in | 3 |
| 12 ft | 12 ft 4 in | 2 |
Pattern repeat: straight match and half-drop
The pattern repeat is the distance down the paper before the design starts again, printed on the label. The match type says how the design lines up from one strip to the next. Both decide how much of each roll you lose.
- No match (random or free match). Stripes, textures and plain papers line up with any strip. Each strip is just the wall height plus the trim.
- Straight match. The design lines up straight across, so every strip starts at the same point in the pattern. When strips are cut one after another from a roll, each one uses its length rounded up to a whole number of repeats.
- Half-drop match. Every other strip starts half a repeat lower, so the design runs diagonally. Cut in turn from one roll, every strip uses its length rounded up to an odd number of half repeats: 1½, 2½, 3½ repeats and so on.
With an 8 ft wall, 4 in of trim and a straight match with a 21 in repeat, the strip needs 100 in, which rounds up to five repeats: 105 in (8 ft 9 in). A double roll still gives 3 strips. The common shortcut of adding one full repeat to every strip gives 121 in instead. That shortcut is safe but can cost a roll: for the example room it gives 10 rolls instead of 9. The calculator offers both under Strip length.
A half-drop does not always waste more than a straight match. With a 24 in repeat and the same 100 in strip, a straight match cuts each strip at 120 in, while a half-drop cuts at 108 in, because every other strip can start half a repeat further down the roll. On a 96 in strip it is the other way round. On average both lose about half a repeat per strip, so always enter the real match and repeat rather than a rule of thumb. Some installers cut half-drop papers from two rolls at once to save paper; the calculator assumes you cut from one roll at a time, which is the safer count.
Wallpaper roll sizes
Roll sizes are not fixed by law or by a standard you can rely on, so treat the sizes below as common examples and read the label of the paper you are buying. Wide papers and peel-and-stick panels come in many other sizes: choose Custom size and enter the width and length from the label.
| Roll | Width × length | Square feet | Square meters |
|---|---|---|---|
| US double roll | 20.5 in × 33 ft | 56.38 | 5.24 |
| US single roll | 20.5 in × 16.5 ft | 28.19 | 2.62 |
| European standard roll | 53 cm × 10.05 m | 57.33 | 5.33 |
| Wide roll | 70 cm × 10.05 m | 75.72 | 7.04 |
| Extra-wide roll | 106 cm × 10.05 m | 114.67 | 10.65 |
Single vs. double rolls. In the United States, wallpaper is often priced per single roll but packed and sold as double rolls, one continuous piece twice as long. Check which one a price refers to before you compare papers. Short single rolls are wasteful on standard walls: a 16.5 ft roll gives only 1 strip cut at 8 ft 4 in, while the same paper as a 33 ft double roll gives 3. If your paper comes in single rolls, the calculator warns you when that happens.
Doors, windows and other openings
An opening only saves paper where it takes the place of a whole strip. A 36 in door on a 20.5 in roll covers one full strip width, whatever its position; the rest of its width is still a strip that has to be cut and trimmed around the frame. The calculator subtracts one full-height strip for every whole roll width an opening covers, and adds the short pieces it still needs: one above a door, and one above and one below a window. Short pieces are cut like strips, with the trim and the pattern, and come out of the offcut at the end of a roll before a new roll is opened.
An opening narrower than one roll width saves nothing in the strip count, and the calculator says so. The area method still subtracts every opening, which is one more reason it comes out low. Fireplaces, built-in shelves and other large openings can be entered as an extra door or window of the right size.
Accent walls and ceilings
For a single feature wall, choose Accent wall. A wall 14 ft wide and 9 ft high, in a straight-match paper with a 21 in repeat, takes 168 ÷ 20.5, about 8.2, so 9 strips. Each strip needs 9 ft + 4 in = 112 in, rounded up to six repeats: 126 in. A double roll gives 3, so the wall needs 3 rolls. The wall is 126 sq ft.
When walls don't meet at corners, as with an accent wall or a set of separate walls, each wall is rounded up to whole strips on its own. In a whole room, strips are counted around the perimeter instead, because the strip that reaches a corner is cut lengthwise and the rest of it starts the next wall. Counted wall by wall, the example room would need 32 strips and 10 rolls.
Ceilings are papered in strips across the shorter side of the room, which keeps each strip short enough to handle. A 12 × 10 ft ceiling takes 8 strips laid along the 12 ft side, each cut 124 in from the 10 ft side, or 3 per double roll. Tick Also paper the ceiling in Whole room mode to add them to the count. Papering overhead is hard work; consider a professional for anything but a small ceiling.
How much extra wallpaper to buy
The strip count already includes the trim allowance, the pattern waste and the offcut at the end of every roll, so its Extra rolls field starts at 0%. Some reasons to add more anyway:
- Batch numbers. Rolls printed in different runs can differ slightly in color. Buy every roll you need from the same batch, and a spare one now, because you may not find that batch later.
- Mistakes. A torn, creased or misaligned strip has to be replaced. On a first job, a spare roll is cheap insurance.
- Repairs. A spare roll kept in a dry place lets you patch damage years later with matching paper.
- Lining up a new roll. The count assumes you can start cutting close to the top of each roll. If the pattern has to be lined up first, you can lose part of a repeat at the start of a roll.
The extra is applied to the rolls and rounded up. With 10% extra, the example room goes from 9 to 10 rolls.
Metric rolls and measurements
Switch Units to Metric to see areas in square meters, and type lengths in meters or centimeters. A European standard roll, 0.53 m wide and 10.05 m long, gives four strips for a 2.4 m wall with 10 cm of trim, but only three for a 2.5 m wall.
A wall 4 m wide and 2.5 m high takes 4 ÷ 0.53, about 7.5, so 8 strips. Each is cut 2.60 m, a roll gives 3, and the wall needs 3 rolls. The area method would say 10 m² ÷ 5.33 m² rounds up to 2, which is not enough paper to hang eight strips.
| Wall height | Cut length | Strips per roll |
|---|---|---|
| 240 cm | 2.50 m | 4 |
| 250 cm | 2.60 m | 3 |
| 270 cm | 2.80 m | 3 |
| 300 cm | 3.10 m | 3 |
The conversions are exact: since 1959, an inch is exactly 2.54 centimeters and a foot exactly 0.3048 meters, as the National Institute of Standards and Technology (NIST) lists in Handbook 44, Appendix C and Special Publication 811. So a square foot is exactly 0.09290304 square meters, and a square meter is about 10.7639 square feet.
How we calculate
Every figure in the tool and on this page comes from the same code, and the examples above are checked against it automatically.
- Lengths. Every measurement is converted to feet first: inches ÷ 12, centimeters ÷ 30.48, meters ÷ 0.3048, the exact NIST definitions.
- Strips. Strips across a wall = width ÷ roll width, rounded up. In a whole room the widths are added first, so strips are counted around the perimeter. An opening replaces one full strip for every whole roll width it covers.
- Cut length. Drop + trim. With a straight match, rounded up to a whole number of repeats; with a half-drop, rounded up to an odd number of half repeats; with the shortcut, plus one full repeat.
- Rolls. Strips per roll = roll length ÷ cut length, rounded down. Every strip and short piece is then placed, longest first, into the first roll with enough length left, and a new roll is opened only when none has. The extra multiplies the rolls by (1 + extra ÷ 100), rounded up.
- Area method. (Wall area − openings + ceiling) × (1 + extra ÷ 100) ÷ roll area, rounded up to a whole roll.
- Left over. Rolls × roll area − the area covered.
- Cost. Rolls × your price per roll. Nothing is filled in for you, because prices vary from paper to paper.
The calculator does not estimate paste or adhesive. Pre-pasted papers need none, and the amount for paste-the-wall and mixed pastes depends on the product, so follow the label.
Your measurements stay on your device
The calculator runs entirely as JavaScript in your browser tab. Nothing you enter is uploaded: the page's Content-Security-Policy allows connections only back to this site, and the tool has no code that sends anything anywhere. It remembers your last measurements and settings in your browser's local storage, on your device only. There is no account and no cookie.
Frequently asked questions
How many rolls of wallpaper do I need?
Divide the width of the walls by the roll width to get the number of strips, divide the roll length by the strip length (wall height plus trim, matched to the pattern) to get the strips per roll, then divide the strips by the strips per roll and round up. The calculator does this for every wall and adds the short pieces around doors and windows.
How many rolls of wallpaper do I need for a 12 × 12 room?
With 8 ft walls, one door, two windows, no pattern to match and 4 in of trim, it takes 9 US double rolls: 26 full strips at 3 per roll, with the short pieces cut from the offcuts. With 2 in of trim, a roll gives 4 strips and 7 rolls are enough. A patterned paper or taller walls can need more.
How many square feet are in a roll of wallpaper?
Multiply the width by the length on the label. A US double roll of 20.5 in × 33 ft holds 56.38 sq ft, a single roll 28.19 sq ft, and a European roll of 0.53 × 10.05 m holds 5.33 m², or 57.33 sq ft. Not all of it ends up on the wall, because of trimming, pattern matching and the offcut at the end of the roll.
What is the difference between a single roll and a double roll?
A double roll is one continuous piece twice the length of a single roll, for example 33 ft instead of 16.5 ft. Papers are often priced per single roll but sold in double rolls, so check which one a price means. A double roll wastes less, because a longer roll leaves fewer offcuts.
How do I account for the pattern repeat?
Enter the repeat and the match type from the label. For a straight match, each strip's length plus trim is rounded up to a whole number of repeats; for a half-drop, to an odd number of half repeats. The shortcut of adding one full repeat to every strip is also available, and is a little more conservative.
What is a half-drop match?
A pattern in which every other strip starts half a repeat lower than the one beside it, so the design runs diagonally across the wall. You can tell from the label, which shows a match symbol and the repeat. The calculator works out how much of each roll a half-drop strip uses.
Do I subtract doors and windows?
Only where an opening covers at least one whole roll width. The calculator removes one full strip for each whole roll width an opening covers and adds the shorter pieces above it and, for a window, below it. Small windows save nothing, because the strips beside them still run the full height.
How much extra wallpaper should I buy?
The strip count already covers trimming, pattern waste and roll ends, so it starts with no extra. Buying one spare roll from the same batch is wise, for mistakes and later repairs, because a later batch may not match exactly.
How many strips can I get from one roll?
Divide the roll length by the cut length and round down. A 33 ft double roll gives 3 strips for an 8 ft wall with 4 in of trim. A large pattern repeat or taller walls can bring that down to 2 or even 1.
How do I calculate wallpaper for an accent wall?
Choose Accent wall and enter the wall's width and height. A 14 × 9 ft wall in a straight-match paper with a 21 in repeat takes 9 strips, 3 per double roll, so 3 rolls.
Why do wallpaper calculators give different answers?
Some divide the wall area by the roll area, which ignores the offcut at the end of each roll, and others count strips. They also differ in the trim allowance and in how they add the pattern repeat. This calculator shows the strip count, the area method and every assumption, so you can see where the numbers come from.
Sources
- National Institute of Standards and Technology: NIST Handbook 44 (2026), Appendix C, General Tables of Units of Measurement: 1 foot = 12 inches = 0.3048 meter and 1 inch = 2.54 centimeters, exactly.
- NIST Special Publication 811, Appendix B.9, Factors for units listed by kind of quantity: exact factors for the foot and the inch.
- NIST Special Publication 811, Appendix B, Section B.6, on the 1959 definitions of the yard, foot and inch.
- U.S. Environmental Protection Agency: Protect Your Family from Sources of Lead, on lead-based paint in homes built before 1978.
This is an educational tool, not professional decorating or construction advice. Roll sizes, pattern repeats and trim allowances vary: check the label of the paper you buy and the instructions that come with it, and buy all rolls from the same batch.