Wallpaper Calculator
Strips and rolls for walls from room size, roll size, and pattern repeat.
What it does
Wallpaper sells by the roll but hangs by the strip, and pattern matching connects the two. Wall length divided by roll width gives the strip count. Roll length divided by strip length plus one pattern repeat gives strips per roll. Divide and round up twice, and the count is safe.
The tool above runs that path from wall size, roll size, and repeat. It returns strips, rolls, and cost at your roll price.
The repeat is the silent budget line. A plain paper with no match turns nearly the whole roll into wall. A large twelve inch repeat can drop a three strip roll to two, raising the bill by half with no change in room size.
Dye lots matter more than brands admit. Rolls from different lots can shade apart on the same wall, so buy the full count plus one spare from a single lot and keep the labels until the paste dries.
How to use
- Switch the unit system first: imperial for feet and inches, metric for meters and centimeters.
- Add every wall length into one total, ignoring doors for strips.
- Read roll width, length, and repeat off the exact paper label.
- Enter zero repeat for plain, textured, or random match papers.
- Buy the rounded rolls from one lot and keep one spare.
Formula
- wall inches
- Total wall length times 12, since roll width is inches.
- repeat
- Pattern length in inches. Each strip after the first wastes up to one repeat aligning the design.
- floor, ceil
- Round strips per roll down (partial strips are scrap) and rolls up.
- dye lot
- Factory batch code. One lot keeps every strip the same shade.
Doors and windows still consume strips on both sides, so walls measure full length. Only huge openings like sliding glass justify subtracting, and even then keep the spare roll.
Worked example
Example: 40 ft of wall, 8 ft high, 20.5 in rolls, 12 in repeat
Walls 40 ft, height 8 ft, US rolls 20.5 in by 33 ft, 12 in repeat, $60 per roll.
- Wall inches: 40 x 12 = 480.
- Strips: 480 / 20.5 = 23.4, round up to 24.
- Strip length: 96 + 12 = 108 inches.
- Per roll: floor(396 / 108) = 3 strips.
- Rolls: 24 / 3 = 8 rolls.
- Cost: 8 x $60 = $480.00 before paste and tools.
Reference table
| Repeat | Strip length | Strips per roll |
|---|---|---|
| 0 in (no match) | 96 in | 4 |
| 6 in | 102 in | 3 |
| 12 in | 108 in | 3 |
| 18 in | 114 in | 3 |
| 24 in | 120 in | 3 |
Limits
- Straight walls of even height. Slopes, stairs, and dormers need drawing first.
- Treats all walls as full strips. Huge glass walls may overcount by a roll.
- Repeat waste assumes straight match. Half drop matches waste a little more.
- Paste, primer, and tools sit outside roll cost.
Common mistakes
- Measuring area like paint. Wallpaper counts strips, not square feet.
- Ignoring the repeat on bold patterns, then running two rolls short.
- Mixing dye lots across one wall.
- Skipping wall prep. Paste over dust and gloss fails in sheets.
- Ordering exact rolls with no spare for future patches.
Try it yourself
Quick checks. Answers sit tucked under each question.
30 ft of wall, 21 in rolls. Strips?
30 x 12 = 360 inches. 360 / 21 = 17.1, so 18 strips.
18 strips at 4 per roll. Rolls?
18 / 4 = 4.5, so 5 rolls.
Questions
How wide is a standard roll?
US rolls run 20.5 in wide by 33 ft long. EU rolls are usually 53 cm (21 in) by 10 m.
What is pattern repeat?
The vertical length of one full design cycle. Matching it across strips wastes up to one repeat per strip.
Do I subtract doors and windows?
No for normal sizes. Strips run past both sides, and offcuts rarely span openings cleanly.
What is a dye lot?
The factory batch. Same pattern across lots can shade differently, so buy one lot plus a spare.
Can beginners hang wallpaper?
Yes with paste the wall types and no match designs. Large repeats and thin papers punish first timers.
How do I estimate for one accent wall?
Measure that wall only and run the same math. Most accent walls need 2 to 4 rolls.