Example: a 12 × 10 ft room with 8 ft walls, US double rolls
- Wall width to cover: 2 × (12 + 10) = 44 ft, or 528 in.
- Strips: 528 in ÷ 20.5 in per strip = 25.8, so 26 strips.
- Each strip is 8 ft plus about 4 in for trimming, so a 33 ft roll gives 3 full strips.
- Rolls: 26 ÷ 3 = 8.7, so buy 9 double rolls.
How it's calculated
- Strips = total wall width ÷ roll width, rounded up.
- Strip length = wall height + about 4 in (10 cm) for trimming. With a pattern, it's rounded up to a whole number of repeats.
- Strips per roll = roll length ÷ strip length, rounded down — the leftover piece is too short to use.
- Rolls = strips ÷ strips per roll, rounded up.
Assumptions
- This is the strip (drop) method decorators use. It's more accurate than dividing wall area by roll area, which ignores the offcut at the end of every roll.
- Doors and windows aren't subtracted; the pieces around them are rarely cut from usable offcuts, so the difference becomes your spare.
- Pattern repeats are treated as straight matches — every strip starts at the same point in the pattern.
- US wallpaper is priced per single roll but usually sold in double rolls of about 20.5 in × 33 ft.
Frequently asked questions
How many rolls of wallpaper do I need for a 12 × 12 room?
About 10 US double rolls (20.5 in × 33 ft) for 8 ft walls with a plain or random-match paper. A large pattern repeat can add a roll or two.
What's the difference between a single and a double roll?
In the US, wallpaper is priced per single roll (about 28 sq ft) but usually packaged as double rolls (about 56 sq ft, 20.5 in × 33 ft). European rolls are 0.53 × 10.05 m, about 5.3 m².
What is a pattern repeat?
The vertical distance before the design repeats. Every strip has to start at the same point in the pattern so the seams line up, which uses extra paper on each strip. Find the repeat on the label and enter it — each strip is rounded up to a whole number of repeats.
Do I subtract doors and windows?
Not usually. The pieces above and below doors and windows are short and awkward, and the extra gives you a spare for mistakes. For walls that are mostly glass, measure only the papered width and use Wall(s) mode.
Why should all rolls have the same batch number?
Rolls printed in different runs (batches or lots) can differ slightly in color. Buy everything at once, check the batch numbers match, and consider one spare roll for repairs.