Wallpaper Calculator — How Many Rolls Do You Need?
Buying too few rolls is the classic wallpaper mistake — dye lots vary between batches, so you cannot easily top up later. This calculator works out the total wall area, subtracts your doors and windows, and rounds up to the nearest roll.
How we calculate
Wall area = 2 × (length + width) × height. Deduct 1.9 m² per door, 1.2 m² per window. Roll area = width × length. Rolls = ⌈(paperable area ÷ roll area) × (1 + waste %)⌉.
Worked example
Room 4 m × 3 m, 2.4 m walls, 1 door, 1 window, 0.53 m × 10 m rolls, 15% waste. Paperable area ≈ 30.5 m². Roll area = 5.3 m². Rolls = ⌈(30.5 ÷ 5.3) × 1.15⌉ = 7 rolls.
Common mistakes
- •Buying exactly the minimum — always buy one extra roll in the same batch.
- •Using a flat 10% for patterned wallpaper — large repeats waste 25–35% per drop.
- •Measuring only two accent walls and forgetting the full perimeter.