Wallpaper Calculator

How to Use the Wallpaper Calculator

Buying the right amount of wallpaper avoids both shortages and wasted money on unused rolls. Enter your room length, width, and wall height in feet. Specify the number of doors and windows so the calculator can subtract those openings from the total strip count. If your wallpaper has a repeating pattern, enter the vertical pattern repeat distance in inches. The calculator determines the number of wallpaper strips needed, how many strips fit per roll, and the total number of rolls to purchase.

The calculation is based on American single rolls measuring 20.5 inches wide and 33 feet long. Each strip of wallpaper must be at least as tall as your wall height, and the number of strips that can be cut from one roll depends on the wall height and pattern repeat. A pattern repeat means each strip must be cut longer to align the design, which reduces the number of usable strips per roll and increases the total rolls needed.

Understanding Wallpaper Pattern Repeats

Wallpaper patterns are categorized as random match, straight match, or drop match. Random match patterns such as textures and vertical stripes have no repeat and produce the least waste. Straight match patterns align horizontally across adjacent strips at the same height. Drop match patterns offset the design by half the repeat distance on alternating strips, which requires the most careful planning and typically produces the most waste.

Preparing Walls for Wallpaper

Proper wall preparation is essential for a professional-looking wallpaper installation. Walls should be clean, smooth, dry, and primed with a wallpaper-specific primer or sizing. Fill any holes or cracks with spackling compound and sand smooth. Remove old wallpaper completely rather than hanging over it. New drywall must be primed to prevent the wallpaper adhesive from bonding permanently to the paper facing, which would make future removal extremely difficult.

Tips for Ordering Wallpaper

Always order all your wallpaper at once from the same dye lot number. Different print runs can have slight color variations that are noticeable when hung side by side. Most retailers allow returns of unopened rolls, so it is better to buy one or two extra rolls than to run short and risk a dye lot mismatch. Keep one leftover roll stored flat in a cool, dry place for future repairs or patching.

Frequently Asked Questions

How do I calculate how much wallpaper I need?

Measure the room perimeter by adding the length of all walls. Divide the perimeter by the width of one wallpaper strip, typically 20.5 inches for American rolls, to get the total number of strips. Then determine how many strips you can cut from one roll based on wall height and pattern repeat. Divide total strips by strips per roll and round up.

What is a standard wallpaper roll size?

An American single roll is approximately 20.5 inches wide and 33 feet long, covering about 56 square feet before trimming. A European roll is typically 21 inches wide and 33 feet long. Double rolls are twice the length at 66 feet.

How does pattern repeat affect wallpaper quantity?

Pattern repeat is the vertical distance between identical points in the pattern. Each strip must be aligned, so you may need to cut extra paper to match the pattern. A large pattern repeat of 24 inches or more can increase waste by 20 to 30 percent.

Should I subtract doors and windows from wallpaper calculations?

Yes. Each standard door and window saves approximately one wallpaper strip. The calculator subtracts these openings from the total strip count. However, do not subtract for small openings where you may still need a full-width strip.

How many extra rolls of wallpaper should I buy?

Buy at least one extra roll beyond the calculated amount for pattern matching waste, cutting errors, and future repairs. If the wallpaper has a large pattern repeat, buy two extra rolls. Always purchase from the same dye lot.