How the wallpaper calculation works
- Strips around the room. Divide the perimeter by the roll width and round up. That is how many full-height strips you hang.
- Strip length. Wall height plus the pattern repeat, plus a few inches for trimming at the top and bottom.
- Strips per roll. Divide the roll length by the strip length and round down. Leftover pieces are usually too short to use.
- Rolls. Divide the number of strips by strips per roll and round up.
Worked example
A 14 × 12 ft room has a 52 ft perimeter. Remove one door and 49 ft remains. With 20.5 in wide paper, that is 29 strips. On 8 ft walls with no repeat, each strip is about 8 ft 4 in, so a 33 ft double roll gives 3 strips. 29 ÷ 3 = 9.7, so buy 10 double rolls.
What is pattern repeat?
The repeat is the vertical distance before the pattern starts again. To line the pattern up across strips, each strip has to start at the same point in the design, which wastes paper. The repeat is printed on the label, often with a symbol showing whether it is a straight match or a drop match. Plain and random-match papers have no repeat: enter 0.
US rolls and metric rolls
In the US, wallpaper is often priced per single roll but sold only in double rolls. A double roll is about 56 sq ft of paper. In Australia, Canada and Europe, the common roll is 53 cm by 10.05 m, about 5.3 m². Always check the label, because sizes vary by brand.
Tips before you order
- Buy all rolls from the same batch or lot number. Colours can differ slightly between batches.
- Buy one extra roll for mistakes and future repairs, especially with large repeats.
- Prime or size bare walls so the paper slides into place and can be removed later.
Frequently asked questions
How many rolls of wallpaper do I need for a 12 × 12 room?
With 8 ft walls, one door and no pattern repeat, a 12 × 12 room needs about 27 strips of 20.5 in paper. At 3 strips per roll, that is 9 US double rolls.
Do I subtract windows when wallpapering?
Usually not. You still hang short strips above and below windows, so most people subtract only doors and large openings.
What does a drop match mean?
In a drop match, the pattern on alternate strips is shifted down by half a repeat. It often uses more paper than a straight match.
Last updated November 1, 2026.