📚 What's in This Guide
This wallpaper calculator tells you how many rolls to buy for a room, and it handles pattern repeat, which most quick estimates ignore. Enter each wall, choose or type your roll size, pick the pattern match, and it lays the strips along the roll the way a decorator would. You get the rolls to buy, the strips, the cut length, and an optional cost. It works in inches, feet, yards, centimeters, and meters, so it also serves as a wallpaper estimator, a wallpaper roll calculator, and a wallcovering calculator.
Below you will find the method, measuring steps, an explanation of pattern repeat and match, common roll sizes, worked examples, and why a square footage estimate can leave you short.
Wallpaper is bought by the strip, not by the square foot. Strips = wall width ÷ roll width, rounded up. Each strip is the wall height plus trim, rounded up to the pattern repeat. Rolls = strips ÷ strips per roll, rounded up.
1. How the Wallpaper Calculator Works
A roll of wallpaper is a long, narrow band. A wall is covered by hanging vertical strips side by side, and each strip must be cut longer than the wall is high, to allow for trimming at the ceiling and the floor. The calculator follows the same steps you would use by hand.
First it divides each wall's width by the roll width and rounds up, because a part strip still uses a full strip of paper. Next it works out the length of each strip, which is the wall height plus your trim allowance. For a patterned paper, it then places the strips along the roll so that the pattern lines up. In a straight match every strip starts on a repeat boundary. In a half-drop match every other strip starts half a repeat later. Finally it counts how many strips fit on one roll, divides, and rounds up. A spare allowance adds extra strips for mistakes.
Besides the rolls to buy, the results show the rolls needed without spare, the number of strips, strips per roll, the cut length, the paper you will buy, the wall area covered, the share of paper left unused, and a quick area-based estimate for comparison. A breakdown table lists every wall, and a step-by-step block shows the math.
The calculator assumes standard vertical hanging, even walls, and rolls whose pattern starts at the same point on every roll. It does not handle murals, panels, borders, or walls that slope. Pattern matching around corners can add waste that no calculator can predict. Treat the result as a planning estimate and confirm it with your supplier or installer.
2. How to Use the Wallpaper Calculator
- Choose imperial units (feet and inches) or metric units (meters and centimeters).
- Enter each wall's width and height. For a plain rectangular room, use Quick Room to create four walls from the length, width, and height.
- Pick your roll size from the list, or type the width and length from the label. In imperial mode, roll length can be in feet or yards.
- Choose the pattern match and enter the pattern repeat from the label. For a free (random) match, no repeat is needed.
- Check the trim allowance, which is the extra length added to every strip for trimming at the ceiling and the floor.
- Set the spare allowance. It defaults to 10 percent.
- Leave doors and windows on Hang across, or choose Deduct and enter each opening to see an estimate.
- Optionally enter the price per roll, then read the rolls to buy, the strips, the breakdown, and the step-by-step math.
- Use Copy Result, Share Result, or Download PDF to keep the numbers, and Reset All to start again.
If a measurement is missing, a fraction cannot be read, or a strip is longer than the roll, the calculator tells you which input needs attention instead of showing a number.
3. How to Calculate Wallpaper Needed
Strips per wall = wall width / roll width, rounded up
Strip length = wall height + trim
Strip step (straight match) = strip length rounded up to a multiple of the repeat
Strips per roll = rounded-down ((roll length - strip length) / step) + 1
Rolls = total strips / strips per roll, rounded up
These formulas describe a straight match with walls of one height. The calculator does not rely on a single formula: it lays the strips along the rolls, keeping the pattern aligned, so half-drop matches, walls of different heights, and short pieces are handled by the layout itself. For straight and free matches, a shorter strip can use leftover length at the end of an earlier roll. For a half-drop it keeps the strips in the order you would hang them, which is the more cautious choice. In those cases the number of strips can vary from roll to roll.
The strips-per-roll line reflects that the last strip on a roll only needs its own length, not the rounded-up step, so it can sit right at the end of the roll. A simpler hand method adds one full repeat to the strip length and divides the roll length by that, which is slightly more cautious, and the spare allowance covers the difference.
Part strips count as whole strips. Wallpaper should not be turned fully into a corner, because walls are rarely straight and the paper can crease, so the part-width left over at a corner is calculated as a full strip, as James Dunlop's wallpaper calculation guide explains. That guide also adds trim to each strip and rounds the roll count up with extra for pattern waste, which is the same sequence the calculator follows.
4. How to Measure a Room for Wallpaper
- Measure each wall separately. Measure from corner to corner at the widest point. Do not add the walls together, because every wall rounds up to whole strips.
- Measure the height of the area you will paper. Go from the ceiling, or the coving, down to the top of the baseboard, or to the floor if you will paper that far.
- Use the largest measurement. Walls and ceilings are rarely perfectly level, so measure the height in a few places and use the tallest.
- Note every opening. You only need sizes if you plan to deduct them, but it helps to write them down.
- Read the label. Find the roll width, roll length, pattern repeat, and match type on the label or product page.
5. Pattern Repeat and Pattern Match
These two terms are often mixed up. The pattern repeat is the vertical distance before the design repeats. The pattern match describes how the design lines up from one strip to the next.
| Match type | How strips line up | Effect on paper |
|---|---|---|
| Straight match | The pattern meets at the same height on every strip. | Each strip starts on a repeat boundary, so some paper is lost at the top of each strip. |
| Half-drop match | Every other strip starts half a repeat lower, so the design steps down diagonally. | Often needs more paper than a straight match, especially with a large repeat, though not in every layout. |
| Free (random) match | Strips can be hung in any order with no matching. | No repeat allowance, so the least waste. |
A larger repeat wastes more paper, because up to one repeat can be lost on each strip. The same repeat can need more rolls in a half-drop than in a straight match, as the examples below show. For papers with a repeat up to about 26 cm (10 inches), guides commonly suggest about 10 percent extra, and 15 to 20 percent for larger repeats.
6. Roll Sizes and Units
Roll sizes differ by country and by product, so always use the numbers on your label. These are the sizes built into the calculator.
| Roll | Width x length | Common use |
|---|---|---|
| US double roll | 20.5 in x 33 ft (about 56 sq ft) | Sold as a double roll, which is two single rolls on one bolt |
| US single roll | 20.5 in x 16.5 ft | Priced per single roll |
| UK/EU standard | 53 cm x 10.05 m | Most rolls sold by the roll in the UK and Europe |
| UK retail | 52 cm x 10 m | Common retailer size |
| Wide | 72 cm x 10 m | Wide-width papers |
| Wide roll | 27 in x 30 ft | Some designer and traditional papers |
| Peel and stick | 27 in x 18 ft | Self-adhesive rolls |
| Pre-pasted | 24 in x 30 ft | Papers with paste already on the back |
Some wallcoverings are sold by the yard or meter, not by the roll. For those, choose Custom, enter the width, and set the length to a long bolt in yards. Useful conversions are 1 yard = 3 feet = 36 inches = 91.44 cm, 1 inch = 2.54 cm, and 1 square meter = 10.7639 square feet.
7. Doors and Windows
It seems logical to subtract doors and windows, but the paper does not behave like a simple area. Strips still run across the top of a door and above and below a window, and the pieces must match the strips beside them. Some guides therefore recommend treating a wall with openings as a full wall. Others subtract large openings.
The calculator offers both. By default it hangs paper across openings, which is the safer choice. If you choose Deduct, you enter each opening's width, height, and the height of its bottom edge from the floor. It then removes the strips that fall completely inside the opening and adds short pieces for the paper above and below it, with one extra repeat allowed for matching on each piece. This is an estimate. If you deduct openings, keep a spare roll in case the short pieces cannot be cut from the offcuts.
8. Worked Examples
A feature wall in feet and inches
A wall is 12 ft wide and 9 ft high. The paper is a US double roll, 20.5 in by 33 ft, with a 12 in straight-match repeat. The trim allowance is 6 in and the spare allowance is 10 percent.
| Step | Calculation | Result |
|---|---|---|
| Strips | 144 in / 20.5 in = 7.02 | 8 strips |
| Strip length | 108 in + 6 in | 114 in |
| Step on the roll | 114 in rounded up to a multiple of 12 in | 120 in |
| Strips per roll | 396 in roll: starts at 0, 120, and 240 in; a fourth would start at 360 in | 3 strips |
| Rolls | 8 / 3, rounded up | 3 rolls |
| With spare | 8 x 1.10 = 8.8, rounded up to 9 strips | 3 rolls |
Notice that the wall is 12 ft wide, and 144 inches divided by 20.5 gives just over 7 strips, so an eighth strip is needed for a thin sliver. That is the kind of detail an area-based estimate cannot see.
A half-drop makes a difference
A wall is 12 ft wide and 10 ft high. The paper is a US double roll with a 16 in repeat and a 6 in trim. With a straight match the wall needs 3 rolls, and 3 with spare. With a half-drop match it needs 4 rolls, and 5 with the 10 percent spare, because every other strip starts half a repeat later and fewer strips fit on each roll. Choose Half-drop in the calculator and compare.
A room in meters, with and without a pattern
A room is 4 m by 3 m with 2.3 m walls. The paper is 53 cm by 10.05 m, the trim is 15 cm, and the spare allowance is 10 percent. The four walls need 8 + 6 + 8 + 6 = 28 strips, since 400 / 53 = 7.5 rounds up to 8, and 300 / 53 = 5.7 rounds up to 6.
| Paper | Strips per roll | Rolls needed | With 10% spare |
|---|---|---|---|
| Free match, no repeat | 4 | 7 | 8 |
| Straight match, 64 cm repeat | 3 | 10 | 11 |
The walls and the room are exactly the same, but the 64 cm repeat adds three rolls. With a strip length of 245 cm, a repeat of 64 cm makes each strip use 256 cm of the roll, so only 3 strips fit in 10.05 m instead of 4.
The same room with a door and a window
Add a door 90 cm wide and 200 cm high to the 4 m wall, and a window 120 cm wide and 120 cm high, 90 cm above the floor, to a 3 m wall. If you choose Deduct, the calculator replaces 3 full strips with 5 short pieces, which reduces the straight-match room from 10 rolls to 9, or from 11 to 10 with spare. If you keep Hang across, it stays at 10 rolls, or 11 with spare. The saving is real but small, and it depends on being able to match the short pieces.
9. Why Square Footage Can Mislead
Many tools divide the wall area by the area of a roll. That is fine for plain paper, but it ignores two things: strips cannot be split, and the pattern repeat wastes paper. In the room above, the walls come to 32.2 square meters. A roll of 53 cm by 10.05 m covers 5.33 square meters, so an area estimate gives about 7 rolls, even with a 10 percent spare. The straight-match paper actually needs 10 to 11. The calculator shows this area-based figure next to the real result so you can see the gap.
A US double roll of 20.5 inches by 33 feet is about 56 square feet on paper, but you will rarely cover that much wall with it, since each strip loses length to trim and pattern. If you need wall area itself, for example for paint, our Square Footage Calculator adds up walls and subtracts openings. For wallpaper, count strips.
10. Buying Tips
- Buy all your rolls at once and check that they carry the same batch or dye lot number. Colors can differ between batches.
- Allow more spare for large repeats, half-drop matches, and out-of-square walls. About 10 percent suits small repeats, and 15 to 20 percent suits large ones.
- Keep a spare roll for repairs, especially if the pattern may be discontinued.
- Check whether the price is per single roll or per double roll, and whether the length on the label is per roll as sold.
- If you are unsure, ask your supplier or installer, especially for a complicated room.
11. Common Mistakes
- Using square footage for patterned paper. It ignores strips and repeat.
- Adding all the walls together. Each wall rounds up to whole strips on its own.
- Forgetting trim. Strips must be longer than the wall height.
- Mixing up repeat and match. The same repeat uses more paper in a half-drop.
- Using the wrong roll length. A double roll is twice a single roll, and the label tells you which you are buying.
- Mixing units. Do not enter inches in a field set to centimeters.
- Deducting every opening. It can leave you short.
- Ordering the exact number. Add a spare allowance.
12. Related Calculations and Use Cases
The same method works for feature walls, whole rooms, hallways, and stairwells, as long as you enter each wall separately. For a sloped ceiling or a gable end, use the tallest height of each wall, and expect extra waste. Murals and panel designs are sold by the panel, and need their own dimensions, so this calculator does not cover them.
13. Frequently Asked Questions
Work out how many strips (drops) each wall needs by dividing its width by the roll width and rounding up. Each strip is as long as the wall height plus a trim allowance, rounded up to the next pattern repeat if the paper has a match. Divide the roll length by the strip length, rounding down, to get strips per roll, then divide the total strips by strips per roll and round up. Add a spare allowance for mistakes.
It depends on the room, the roll size, and the pattern. For a room 4 m by 3 m with 2.3 m walls, 53 cm by 10.05 m rolls, and a 64 cm straight-match repeat, you need 10 rolls, or 11 with a 10 percent spare allowance. The same room in a paper with no repeat needs 7 rolls, which is why the pattern matters as much as the wall area.
Round each strip's length up so that the pattern lines up at the same height on every strip. In a straight match, each strip starts on a repeat boundary along the roll. In a half-drop match, every other strip starts half a repeat later. The calculator lays the strips along the roll for you, so you only need to enter the repeat from the label and choose the match type.
Pattern repeat is the vertical distance before the design repeats itself. Pattern match is how strips line up side by side, such as straight, half-drop, or free (random). Two papers with the same repeat can need different amounts of paper if one is a straight match and the other is a half-drop. Free match papers can be cut straight from the roll with no repeat allowance.
Measure each wall's width from corner to corner at its widest point, and its height from the ceiling to the top of the baseboard, or to the floor if you are papering that far. Use the largest measurement on each wall, since walls and ceilings are rarely perfectly level. Write down each wall separately instead of adding them together, because each wall rounds up to whole strips.
Usually not. Strips still run across and around openings, and the paper above doors and below windows is often cut from material you could not otherwise use, so deducting the full area tends to leave you short. Many decorators treat walls with openings as full walls. The calculator hangs paper across openings by default, and an optional mode shows an estimate if you deduct them.
A common guide is about 10 percent extra for papers with a small repeat (up to about 26 cm), and 15 to 20 percent for larger repeats, plus any spare roll you want for repairs. Buy all rolls together, and check that they share the same batch or dye lot number, because colors can vary between batches. The calculator's spare allowance defaults to 10 percent, and you can raise it.
Conclusion
This wallpaper calculator counts strips the way a decorator does, so the pattern repeat, the match type, and the roll length all show up in the answer. Enter each wall, check the roll details against your label, keep a sensible spare allowance, and treat the result as a planning estimate. Compare it with the area-based figure to see why patterned paper needs more than the square footage suggests, and confirm the final quantity with your supplier or installer before you order.
This calculator is for planning purposes only. Roll sizes, repeats, and trimming needs vary by product and installer. Confirm quantities with your supplier or installer before ordering.