Enter your room size, the roll dimensions and the pattern repeat, and get the exact number of wallpaper rolls to buy - using the decorator's drop method that accounts for pattern matching. Works in feet or metres.
A trim allowance of ~10 cm (4 in) per drop is included. Leave doors and windows out to order safely - most decorators don't deduct them, since the offcuts double as the pattern-matching allowance. Add them per room (left) only if you want to trim the count; the deduction is conservative and counts whole drops of freed wall only.
Wall perimeter
18.0 ft
Drops needed
34
Drops per roll
3
The calculator uses the decorator’s drop method rather than dividing the wall area by the roll area, because wallpaper waste comes from two things a simple area sum hides: part-width offcuts at the end of each wall, and the pattern repeat.
drops needed = room perimeter ÷ roll width (rounded up)
drop length = wall height + trim, rounded up to a whole pattern repeat
drops per roll = roll length ÷ drop length (rounded down)
rolls = drops needed ÷ drops per roll (rounded up, per room)
The perimeter is 2 × (length + width). A ~10 cm (4 in) trim allowance is added to every drop for trimming top and bottom. Each room is rounded up to whole rolls on its own - rooms can differ in height (and so in usable drops per roll), and you should not carry a part-roll between rooms because dye lots vary.
Doors and windows are left in by default. If you add their dimensions to a room, the calculator deducts only whole drops’ worth of freed wall - opening area ÷ (roll width × wall height), rounded down - because a fractional offcut can’t be relied on as a reusable drop, especially with a pattern repeat. So a single small window saves nothing, and you’re never short by a part-offcut.
This example follows the unit system you pick in the calculator above.
A 16 ft × 13 ft room with 8 ft walls, papered with a 1.74 ft × 33 ft roll and a 1.7 ft pattern repeat:
On a plain paper with no repeat the drop is only 8.33 ft, so a roll gives 3 drops - buy the same way, and always check the dye-lot number matches across every roll.
| Figure on the label | What it means | Where it goes |
|---|---|---|
| Roll width | Width of one drop | Roll width field |
| Roll length | Total length on the roll | Roll length field |
| Pattern repeat | Vertical distance before the design repeats | Pattern repeat field |
| Match (free / straight / offset) | How drops line up | Free match → set repeat to 0 |
| Batch / dye-lot number | Print-run identifier | Check it matches on every roll |
A 12ft × 12ft room with 8ft walls has a 48ft perimeter - about 28 drops with a standard roll. With a patterned paper you get roughly 3 usable drops per roll, so you need about 10 standard rolls. A plain paper stretches further. Enter your exact room size, roll dimensions and pattern repeat above for a precise count in feet or metres.
By drops. A wall is hung in full-height vertical strips called drops, each the width of the roll, so the count depends on the room perimeter and roll width - not just the area. The last drop on each wall is usually a part-width offcut you cannot reuse, which is why this calculator counts whole drops per room rather than dividing area by roll area.
The pattern repeat is the vertical distance before the design starts again, printed on the roll label. Every drop must begin at the same point in the pattern, so each one is cut to the next whole repeat above your wall height. A large repeat wastes more paper per drop and can add several rolls to a job - which is exactly why it is a separate input here. Set it to 0 for a plain or free-match paper.
Usually not. You still hang short drops above and below doors and windows, and the pattern has to continue across the wall, so those offcuts double as your pattern-matching allowance - and deducting openings is the classic way to run short. This calculator leaves them out by default. If you do want to trim the estimate, you can add each opening's width and height per room: it then removes only whole drops of freed wall and floors the result, so a single small window saves nothing and you are never under-ordered by a fractional offcut.
Wallpaper colour varies slightly between print runs, so two rolls from different batches can show a visible seam. Buy all your rolls - plus a spare - in one go and check the batch or dye-lot number matches on every roll. The calculator rounds up per room so you always have whole rolls, but it is worth adding one extra for future repairs.
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