How to use the wallpaper calculator
- Measure the total width of the walls you will paper. For a whole room, this is the perimeter: a 12 × 14 ft room has 12 + 14 + 12 + 14 = 52 ft of wall.
- Measure wall height from floor (or top of baseboard) to ceiling (or bottom of crown molding).
- Count doors and windows. The calculator assumes about 21 sq ft per door (3 × 7 ft) and 15 sq ft per window (3 × 5 ft), and only deducts whole strips.
- Enter the roll size from the label. Most US wallcoverings are sold as double rolls about 20.5 in × 33 ft; European rolls are 0.53 × 10.05 m (about 20.9 in × 33 ft).
- Enter the pattern repeat printed on the label (in inches or cm). Use 0 for plain or random-match paper.
The strip method, explained
Dividing wall area by roll area underestimates wallpaper, because you cannot use the short leftover at the end of each roll. Instead:
Drop length = wall height + 4 in trim allowance, rounded up to a multiple of the pattern repeat
Strips per roll = roll length ÷ drop length, rounded down
Strips needed = wall width ÷ roll width, rounded up, minus strips saved by openings
Rolls = strips needed ÷ strips per roll, rounded up
The 4-inch allowance gives you 2 inches to trim at the ceiling and 2 at the floor. Large repeats waste more because each strip must start at the same point in the pattern.
Worked example
A 12 × 14 ft bedroom with 8 ft ceilings, one door and two windows, using US double rolls (20.5 in × 33 ft) with no pattern repeat and 5% extra:
- Drop length: 96 + 4 = 100 in
- Strips per roll: 396 ÷ 100 = 3.96 → 3 strips
- Strips for the walls: 624 in ÷ 20.5 = 30.4 → 31 strips
- Openings: 21 + 15 + 15 = 51 sq ft; each strip covers 100 × 20.5 ÷ 144 = 14.2 sq ft, so 3 strips are saved → 28 strips
- Rolls: 28 ÷ 3 = 9.33; with 5% extra = 9.8 → 10 double rolls
With a 25-inch pattern repeat the drop becomes 100 in (already a multiple of 25), but with a 21-inch repeat it becomes 105 in, which still gives 3 strips per roll. Try your repeat in the calculator; it can change the answer by a roll or two.
Single, double and European rolls
US wallpaper is priced "per single roll" but often sold only in double rolls. A US single roll is about 27 sq ft and a double roll about 56 sq ft. Check whether the price and the quantity in your cart refer to the same unit before you order.
Tips for buying wallpaper
- Same batch number. Like tile, wallpaper is printed in runs. Buy all rolls with the same batch (dye lot) number, plus one spare.
- Accent wall? Enter just that wall's width. A 12 ft wall at 8 ft high with no repeat needs 8 strips, or 3 double rolls.
- Drop match patterns (half-drop) alternate between two starting points; allow extra, about 10%.
- Prime first. A wallpaper primer makes installation easier and later removal much easier.
Frequently asked questions
How many rolls of wallpaper do I need for a 12 × 12 room?
With 8 ft ceilings, no repeat, one door and one window, the 48 ft perimeter needs 29 strips minus 2 for openings; at 3 strips per US double roll that is 9 double rolls, or 10 with a small allowance.
How much does one roll of wallpaper cover?
A US double roll (20.5 in × 33 ft) is about 56 sq ft and a European roll about 57 sq ft, but usable coverage is lower after trimming and matching, often 45–50 sq ft.
What is pattern repeat on wallpaper?
It is the vertical distance before the design repeats. Each strip must start at the same point in the pattern, so a larger repeat leaves more waste per strip.
Should I subtract doors and windows?
Only whole strips. Strips above and below windows and above doors still need paper, so this calculator deducts only the full-strip equivalent of the openings.
Is it better to buy an extra roll?
Yes. A spare roll from the same batch costs much less than a mismatched repair later, and many stores accept unopened returns.