Wallpaper has one advantage over paint: the maths is the same, but the penalty for guessing is higher, because mismatched pattern and dye lots are impossible to hide. A little arithmetic saves a lot of frustration.
Area first, rolls second
Start with the wall area — perimeter times height — then subtract openings. Divide by the coverage per roll and add waste for trims and pattern matching. The result is a count of whole rolls, because you can't buy a fraction of one.
Why pattern repeat changes everything
With a repeating pattern, each drop must line up with the previous one, which wastes a strip at the top or bottom of every piece. Busy, large-repeat papers can waste 20–30% — worth folding into the estimate before you buy.
Batch numbers and returns
Wallpaper is dye-lotted, so the same design from different batches can look different. Buying your full quantity at once — plus a roll for mistakes — and keeping the receipt is cheap insurance.
Frequently asked questions
Total your wall area (perimeter × height), subtract doors and windows, add a waste allowance, and divide by the coverage per roll — about 5 m² or 28 ft². This calculator does the whole sum.
10% is a good baseline, rising to 20–30% for large pattern repeats that must be matched across drops.
Yes — manufacturers print the net usable coverage per roll, which already accounts for typical trims. Use that figure when available for the most accurate count.