Wallpaper Calculator
Calculate how many rolls of wallpaper you need to paper a room. Includes a standard waste allowance.
How to use this tool
- Enter room length, width, and wall height in feet.
- Check your wallpaper roll dimensions and enter them accurately.
- Add 15% waste for patterned wallpaper, 10% for plain designs.
Calculate the number of wallpaper rolls needed for any room before you buy.
Formula
Wall area = 2 × (length + width) × height
Roll area = (roll_width ÷ 12) × roll_length
Rolls needed = ⌈(wall_area ÷ roll_area) × (1 + waste% ÷ 100)⌉
How it works
This calculator finds the total paintable wall area by computing the room perimeter (twice the sum of length and width) multiplied by the wall height. That area is divided by the usable area of one wallpaper roll, then rounded up to a whole number after applying a user-specified waste percentage to account for pattern matching, offcuts, and mis-cuts.
Assumptions: the room is a simple rectangle and no deductions are made for doors or windows, which keeps the estimate slightly generous — a common practice to avoid running short mid-project.
Worked example
Worked example
- Room perimeter = 2 × (14 + 12) = 52 ft.
- Wall area = 52 × 9 = 468 ft².
- Roll area = (27 in ÷ 12) × 27 ft = 2.25 × 27 = 60.75 ft² per roll.
- Raw rolls needed = 468 ÷ 60.75 = 7.70 rolls.
- With 15% waste: 7.70 × 1.15 = 8.86, rounded up to 9 rolls.
Rolls needed: 9
Key terms
- Perimeter
- The total distance around the outside of the room, calculated as 2 × (length + width). Used to find how much wall surface needs to be covered.
- Roll coverage
- The surface area that one wallpaper roll can cover, equal to roll width × roll length (both in the same unit).
- Waste allowance
- An extra percentage added to the calculated quantity to account for pattern repeats, mis-cuts, and offcuts at corners or edges.
- Pattern repeat
- The vertical distance after which a wallpaper design repeats itself. Larger repeats increase waste because strips must be aligned before cutting.
- Ceiling function (⌈⌉)
- Rounding up to the next whole number. Used so you always buy enough complete rolls rather than a fractional one.
Frequently asked questions
- How many rolls of wallpaper do I need?
- Divide the total wall area by the coverage per roll, then add 10–15% for waste and pattern matching. Measure wall area as perimeter × height.
- What size is a standard wallpaper roll?
- US double rolls are typically 27 inches wide and 27 feet long, covering about 60 sq ft before waste. European rolls are often 20.5 in × 33 ft.