Wallpaper Calculator
Enter the total wall width you're papering, the ceiling height and your pattern repeat. The calculator uses the strip method — how many drops fit a roll — which is far more accurate than dividing by area.
Results
How the wallpaper calculator works
Dividing wall area by roll area badly underestimates wallpaper, because every drop has to start at the ceiling and match the pattern — the offcut at the bottom is usually wasted. The accurate way is the strip method: work out how many vertical strips (drops) you need, then how many whole strips you can cut from one roll.
Formula: strips = ceil(total wall width ÷ roll width), strips per roll = floor(roll length ÷ (wall height + pattern repeat)), rolls = ceil(strips ÷ strips per roll)
| Roll | Width | Length | Area |
|---|---|---|---|
| US double roll | 20½" | 33 ft | ≈ 56 sq ft |
| US single roll | 20½" | 16.5 ft | ≈ 28 sq ft |
| Euro roll | 20.8" | 33 ft | ≈ 57 sq ft |
US wallpaper is usually sold as "double rolls" even when priced by the single — you'll get one long bolt. Always order in whole rolls.
Pattern repeat and waste
- A pattern repeat is the vertical distance before the design starts again. A big repeat means more waste — each strip is cut longer so the pattern lines up with its neighbor.
- Enter the repeat in inches and the calculator lengthens every drop accordingly, which often knocks one usable strip off each roll.
- Small openings are deliberately left in as a safety margin — the offcuts above and below a window rarely help elsewhere.
- Buy every roll from the same run (batch or lot number). Different batches can shade slightly, and the seam will show it.
Frequently asked questions
How many rolls of wallpaper do I need for a 12x12 room?
A 12 × 12 ft room with 8 ft ceilings has about 48 ft of wall. With plain (no-repeat) US double rolls, that's around 8 rolls — 29 strips at 4 strips per roll. A large pattern repeat can push it higher.
How do I calculate wallpaper rolls?
Divide the total wall width by the roll width to get the number of strips, work out how many whole strips fit a roll (roll length ÷ (wall height + pattern repeat)), then divide the strips by strips-per-roll and round up.
Should I subtract doors and windows for wallpaper?
Usually no. Leaving small openings in builds a helpful waste margin, since the short offcuts above and below them rarely fit elsewhere. Only subtract for very large openings like a wall of glass.
Why does pattern repeat waste wallpaper?
Each strip has to line up with the one beside it, so on a patterned paper you cut every drop a little longer — up to one full repeat — and discard the offcut. The bigger the repeat, the more you lose per strip.