Wallpaper Calculator
Calculate the exact number of wallpaper rolls needed to cover your walls, factoring in roll width, length, and pattern alignment repeats.
Estimated Wallpaper Rolls Needed
0 Rolls
Wall Area: 0 sq ft
How to Calculate Wallpaper Rolls
Wallpaper is sold in rolls, with the standard US double roll measuring **20.5 inches wide by 33 feet long**, covering roughly 56 square feet. Because you have to match pattern designs at the seams, you must account for pattern repeats, which create wasted paper.
The Wallpaper Calculation Method
Here is how the math works:
- Count the Strips: Divide the total wall length by the wallpaper roll width (in feet). For a 15-foot wall and a 20.5-inch (1.7-foot) roll, you need 15 / 1.7 = 9 vertical strips.
- Adjust for Pattern Repeat: A pattern repeat determines how often a design repeats on the vertical roll. If you have an 18-inch pattern repeat, each vertical strip cut must be the wall height plus the repeat value (e.g. 8 ft + 1.5 ft = 9.5 ft) to ensure alignment.
- Strips per Roll: Divide the total roll length by the adjusted strip height. 33 feet / 9.5 feet = 3.47. In practice, you get 3 usable strips out of that roll, and the remainder is waste.
- Calculate Rolls: Divide the total strips needed by the usable strips per roll. 9 strips / 3 strips per roll = 3 rolls. Add a 10% waste cushion for safety.
Frequently Asked Questions
Most wallpapers are priced as "single rolls" but packaged and sold in continuous "double rolls" (33 feet long) to minimize waste. Always verify the roll length and width on the packaging before calculating rolls.
Unless a door or window is huge (like sliding patio doors), we recommend **not** subtracting them from your wall area. The cuts around doors and windows generate matching scrap area, and keeping them in the calculation gives you a safe margin for errors.