Understanding Wallpaper Roll Calculations
Wallpaper is almost always sold in **single rolls** but often packaged as **double rolls** for convenience. The true complexity in estimation comes from the **pattern repeat**, which determines how much usable material you lose when cutting strips to align the pattern across seams.
The Pattern Match Factor
- **Pattern Repeat:** The distance between the repeating design elements. If the repeat is 21 inches, every strip you cut must be at least that much longer than the wall height to ensure a match.
- **Calculating Usable Drops:** The usable area of a roll is calculated by determining how many full, matched strips (or "drops") you can cut from its length. This requires rounding the necessary strip length *up* to the nearest full pattern repeat.
- **Net Area:** Total wall area minus the area of any openings (doors, windows, etc.).
Important: Single vs. Double Rolls
Always confirm with your retailer whether the product is sold in single or double rolls. If buying double rolls, simply divide the $\mathbf{Total\ Single\ Rolls}$ result by two. **Most online retailers and products list square footage based on a Single Roll.**