1. How do you calculate how much wallpaper you need?
Calculating wallpaper requires finding the total surface area of your walls and dividing it by the usable area of a single wallpaper roll. The process is:
- Step 1: Find Wall Area: Multiply the width of each wall by the height. For a full room, find the perimeter (all widths added) and multiply by height.
- Step 2: Deduct Openings: Subtract the area of doors and windows (we use standard deductions of 21 sq ft per door and 12 sq ft per window).
- Step 3: Account for Waste & Patterns: Add a waste margin for trimming. If your wallpaper has a pattern, you must add the pattern repeat length to the height of your wall before calculating area to ensure the design aligns.
2. What is a Pattern Repeat?
Unless you are installing a solid color or a random texture (like grasscloth), your wallpaper will have a repeating design. When hanging the next strip, you have to shift the paper up or down so the design matches perfectly at the seam. This creates unusable scrap at the top or bottom of the roll. Input the "Pattern Repeat" listed on the wallpaper label into our calculator to accurately budget for this lost material.
3. Standard Roll Sizes Explained
Wallpaper terminology can be confusing because it is often priced as a "Single Roll" but packaged and sold as a "Double Roll".
- US Double Roll: Typically 27 inches wide by 27 feet long, covering roughly 60 square feet total.
- Euro Roll: Typically 21 inches wide (0.53m) by 33 feet long (10m), covering roughly 57 square feet (5.3m²).
Our calculator lets you select the standard pre-sets or enter custom roll dimensions based on the exact product you are buying.
4. Why add a standard Waste Margin?
Even without a pattern repeat, you will lose material. Installers must leave a few extra inches at the ceiling and baseboard to trim a perfectly straight line. Corners, uneven walls, and simple human error require a buffer. A 10% margin is highly recommended.