Wall coverings
Wallpaper Calculator
Estimate full vertical drops rather than dividing wall area by roll area—the method that prevents pattern matching surprises.
How to calculate it
- Calculate room perimeter from length and width.
- Enter roll width, roll length, and vertical pattern repeat.
- The calculator rounds every drop to a full repeat before counting rolls.
What the calculator is doing
Drop length = ceiling(height ÷ repeat) × repeat; drops per roll = floor(roll length ÷ drop length); rolls = ceil[(perimeter ÷ roll width) × (1 + waste %) ÷ drops per roll].
- When repeat is zero, the entered wall height becomes the drop length.
- The method counts full vertical drops, so it is more conservative than wall area divided by roll area.
- The current estimate treats the repeat as straight match; offset matches require the manufacturer’s instructions.
Buying checklist
- Confirm usable roll width and length, not package dimensions.
- Record straight, offset, or random match and the repeat distance.
- Check batch numbers before opening any roll.
- Map focal walls and the first drop so pattern placement is intentional.
Common mistakes
Dividing wall area by roll area
That assumes every offcut is reusable and ignores the full-height strips installation actually needs.
Ignoring pattern match type
Offset matches may need more material than a simple vertical repeat suggests.
Subtracting every opening
Drops often continue above and beside openings, so the saved material may be much smaller than the opening area.
Frequently asked questions
Why does pattern repeat increase rolls?+
Every strip must begin at a matching point, so part of each roll becomes an unusable offcut. Larger repeats generally create more waste.
Should I subtract doors and windows?+
Large openings can be subtracted for area planning, but full drops around them may still be required. Keep a waste allowance for these cuts.