What this calculator does
This tool estimates how many rolls of wallpaper you need to cover a single rectangular wall. It divides the wall's surface area by the usable area of one roll and rounds up, because you can't buy a fraction of a roll. It works with any unit set as long as you stay consistent — the defaults use metres.
How to use it
Measure your wall's width and height, then check the roll's width and length on its packaging (a common European roll is 0.53 m wide and 10 m long). Enter all four numbers and the calculator returns the total rolls required, along with the computed wall area and the area each roll covers.
The formula explained
The math is straightforward: wall area is width × height, and roll area is roll width × roll length. Dividing the first by the second gives the theoretical number of rolls, and the ceiling function rounds that up to the nearest whole roll. In symbols: $$\text{Rolls} = \left\lceil \frac{\text{Wall Width} \times \text{Wall Height}}{\text{Roll Width} \times \text{Roll Length}} \right\rceil$$
Worked example
Suppose a wall is 4 m wide and 2.5 m tall, giving a wall area of 10 m². A roll is 0.53 m wide and 10 m long, covering 5.3 m². Then $$10 \div 5.3 \approx 1.89,$$ which rounds up to 2 rolls.
FAQ
Does this account for pattern repeat? No. Large pattern repeats waste material, so add an extra roll if your wallpaper has a big repeat.
Should I subtract doors and windows? This calculator uses the full rectangle for a safety margin. You can reduce the wall height or width slightly if you want a tighter estimate.
What about waste and trimming? Rolls are rarely used 100%. Rounding up usually covers normal trimming, but for tricky walls buy one spare roll.
