Calculator + chartEnter your measurements below and it works the answer out.
Patterned wallpaper is bought in whole vertical drops, not by area. Every strip must start at the same point in the pattern, so the usable drop is your wall height rounded up to a whole number of repeats. Area arithmetic under-orders it.
| Roll | Width | Length | Notes |
|---|---|---|---|
| US double roll | 20.5 in | 33 ft | The usual US purchase — one continuous length, not two rolls |
| US single roll | 20.5 in | 16.5 ft | Priced as a single but rarely sold on its own |
| Alternative US | 21 in | 33 ft | Some brands run a wider bolt |
| Wide width | 27 in | 15 ft | Fewer seams, but heavier to hang |
| European | 53 cm (20.9 in) | 10 m (33 ft) | The metric standard; close to a US double roll but not identical |
These are examples of common roll sizes, not a standard — roll dimensions are set by each manufacturer and are printed on the label. Enter your own if the label differs; the calculator works from what you type, not from these.
Why area arithmetic gets this wrong. Dividing wall area by roll area and adding a fixed percentage is how people end up a roll short. Wallpaper hangs in full-height vertical strips, and every strip has to begin at the same point in the pattern. What is cut off the top of each strip is dead paper, and how much that is depends on the repeat, not on a percentage.
The arithmetic that is actually right. Strips = wall width ÷ roll width, rounded up. Adjusted drop = wall height rounded up to a whole number of repeats. Strips per roll = roll length ÷ adjusted drop, rounded down, because a part strip is no use. Rolls = strips ÷ strips per roll, rounded up.
Match type changes the drop. A straight match lines up across the seam, so each drop rounds up to a whole repeat. A drop or offset match staggers alternate strips by half a repeat, so this page adds half a repeat before rounding — a conservative allowance rather than a precise one, because the exact saving depends on how many strips you cut from each roll and in what order. A random match has nothing to line up and needs only a trimming allowance.
Do not deduct ordinary doors and windows. You hang a full strip across an opening and cut around it afterwards, so the strip is still used. Only a full-height opening — a patio door, an open archway — removes strips, and that is what the optional deduction is for.
Buy it all at once. Wallpaper is printed in batches and the dye lot is on the label. A roll bought a month later can be visibly different under daylight, and it will be the seam you look at every day.
Divide the wall width by the roll width and round up for the number of strips. Round the wall height up to a whole number of pattern repeats for the drop length, see how many whole drops fit a roll, then divide. Twelve feet of wall at eight feet high, on a 20.5 in × 33 ft roll with a 21 in repeat, needs three rolls.
Because every strip has to start at the same point in the pattern. With a 21 in repeat, a 96 in wall needs a 105 in drop — five whole repeats — and the extra 9 in is cut off and thrown away on every single strip.
A straight match lines up horizontally across the seam, so neighbouring strips are cut at the same point. A drop or offset match staggers alternate strips by half a repeat, which uses more paper and needs a longer drop allowance.
Not ordinary ones. You hang a full strip over the opening and trim it after, so the strip is consumed either way. Only a full-height opening such as a patio door genuinely removes strips from the count.
One continuous length of about 33 ft, not two rolls in a bag. Wallpaper is priced by the single roll but almost always sold as a double, which is where most of the confusion comes from.
Wallpaper is printed in batches, and color varies slightly between them. Order every roll at once from the same lot number. A roll bought later to finish a wall is the one seam you will always notice.
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