What does this tool do?
Wallpaper is sold in rolls with fixed coverage, so the roll count depends on total wall area and waste for matching. This calculator subtracts openings and adds a 10% allowance.
The Formula
Rolls = ⌈(2 × (Length + Width) × Height − Openings) × 1.1 ÷ Roll coverage⌉Frequently Asked Questions
How much extra wallpaper should I buy?
Ten percent is a reasonable allowance for trimming and pattern matching. Large repeats or rooms with many corners can need fifteen percent or an extra roll.
Do I subtract doors and windows?
Yes, but only the actual opening area. This calculator takes one combined openings figure, so measure each door and window before adding them up.