About the Wallpaper Calculator
This wallpaper calculator tells you how many rolls to buy using the strip (drop) method that paperhangers use. It works out how many vertical strips cover the width of your walls, how long each strip must be once you allow for trimming and for matching the pattern repeat, and how many full strips you can cut from one roll. Offcuts shorter than a full drop are treated as waste, which is why the answer is often higher than a simple area estimate.
Use it before ordering so every roll comes from the same batch (dye lot) — buying a missing roll later can mean a visible color difference. It works for standard American double rolls, European rolls (about 0.53 m × 10 m) and wide or peel-and-stick formats: just enter the roll width and length printed on the label.
Enter the total width of doors and large windows to skip if you want a tighter estimate, or leave it at zero for a safe surplus. Many decorators add one extra roll for repairs.
With the default inputs, the rolls needed is 9. Change any value above to recalculate instantly.
How to use the wallpaper calculator
- 1Measure the width of every wall you will paper and add them up.
- 2Measure the wall height from baseboard to ceiling.
- 3Enter the roll width, roll length and pattern repeat from the wallpaper label.
- 4Optionally enter the width of doors and large windows to skip.
- 5Buy the number of rolls shown (plus one spare) from the same batch.
Formula and method
Wallpaper is hung in vertical strips, so the useful question is how many full-height strips you can cut from each roll. The number of strips is the wall width divided by the roll width, rounded up. Each strip needs the wall height plus about 4 inches for trimming at the ceiling and baseboard, and when the paper has a pattern repeat the strip is rounded up to a whole number of repeats so the pattern lines up with the next strip.
Dividing the roll length by the strip length (rounding down) gives full strips per roll, because leftover pieces are too short to reuse on full walls. The rolls needed is strips divided by strips per roll, rounded up. The waste percentage compares the paper you buy with the wall area actually covered.
- Wall width
- Perimeter of walls to paper minus skipped openings (in)
- Repeat
- Vertical pattern repeat (in); 0 means no rounding
- Roll length
- Length of paper on one roll (in)
Worked examples
12 × 12 ft bedroom with a 21 in repeat
After skipping 6 ft of openings, 42 ft (504 in) of wall needs 504 ÷ 20.5 = 24.6, so 25 strips. Each strip is 96 + 4 = 100 in, rounded up to 5 repeats of 21 in = 105 in. A 396 in roll gives 3 strips, so 25 ÷ 3 rounds up to 9 rolls ($540).
Plain paper, 12 × 16 ft room, 9 ft walls
47 ft of wall is 564 in, needing 28 strips of 20.5 in. With no repeat each strip is 108 + 4 = 112 in, so a 33 ft roll gives 3 strips and you need 10 rolls, $450 at $45 each.
Feature walls with a 25 in repeat and 10 ft ceiling
37 ft of wall needs 22 strips. A 124 in drop rounds up to 5 repeats (125 in), giving 3 strips per roll, so 8 rolls are needed.
Frequently asked questions
How many rolls of wallpaper do I need for a 12 × 12 room?+
With 8 ft walls, a standard 20.5 in × 33 ft double roll and a modest repeat, a 12 × 12 ft room typically needs 8–10 rolls. Large repeats or tall ceilings push the number up because fewer strips fit on each roll.
What is a pattern repeat?+
It is the vertical distance before the design repeats. Each strip has to start at the same point in the pattern as its neighbor, so strips are cut in whole multiples of the repeat, which increases waste.
Should I subtract doors and windows?+
Subtract full-height openings such as doors and patio doors. Many decorators do not subtract small windows because the short pieces above and below them still use a full strip width.
What size is a standard roll of wallpaper?+
In the US wallpaper is priced by the single roll but sold in double rolls, typically 20.5 in wide and about 33 ft long. European rolls are about 0.53 m wide by 10.05 m long, a similar size.
Why buy an extra roll?+
Rolls are printed in batches and color can vary between batch numbers. Buying a spare from the same batch covers mistakes, and it gives you matching paper for future repairs.