Wallpaper Roll Calculator
Enter your room and wallpaper dimensions to estimate how many rolls you'll need for your project.
Wallpaper Roll Details
How to Calculate How Much Wallpaper You Need
Estimating the correct amount of wallpaper for your project is crucial. Too little, and you risk running out mid-job or not being able to find the same dye lot later. Too much, and you've wasted money. This guide and our calculator will help you get an accurate estimate, ensuring your wallpapering project goes smoothly.
Key Factors for Wallpaper Calculation
Several measurements are essential for an accurate estimate:
- Room Dimensions: The length, width, and height of the room determine the total wall surface area.
- Number of Doors and Windows: While you cut around these, the calculation typically assumes full strips are hung and trimmed, as this is safer for pattern matching.
- Wallpaper Roll Width: Standard roll widths vary, but common sizes are 20.5 inches (52 cm) or 27 inches (68.5 cm).
- Wallpaper Roll Length: Rolls are typically sold in lengths like 16.5 feet (5 meters) or 33 feet (10 meters).
- Pattern Repeat: This is the distance between the identical points of a pattern on the wallpaper. A larger pattern repeat means you'll need more wallpaper to ensure the pattern aligns correctly from one strip to the next.
Step-by-Step Calculation Guide
Our calculator uses the following method to determine your wallpaper needs:
1. Measure Your Room
First, measure the length, width, and height of your room in feet. Also, count the number of doors and windows. For example:
- Room Length: 12 feet
- Room Width: 10 feet
- Room Height: 8 feet
- Number of Doors: 1
- Number of Windows: 2
2. Determine Wallpaper Roll Specifications
Check the label of your chosen wallpaper for its width, length, and pattern repeat. For our example:
- Roll Width: 21 inches
- Roll Length: 33 feet
- Pattern Repeat: 24 inches
3. Calculate Room Perimeter
The perimeter is the total distance around the room. We convert room dimensions to inches for consistency with wallpaper measurements.
Room Length (inches) = 12 ft × 12 = 144 inches
Room Width (inches) = 10 ft × 12 = 120 inches
Perimeter (inches) = 2 × (144 + 120) = 2 × 264 = 528 inches
4. Calculate Number of Strips Needed
Divide the room's perimeter by the wallpaper roll's width to find out how many vertical strips you'll need to cover all walls. Always round up to the nearest whole number.
Number of Strips = Ceiling(Perimeter / Roll Width)
Number of Strips = Ceiling(528 inches / 21 inches) = Ceiling(25.14) = 26 strips
5. Account for Pattern Repeat (Effective Strip Height)
This is where pattern repeat becomes critical. For each strip, you need enough length to cover the wall height AND allow for pattern matching. We calculate the smallest multiple of the pattern repeat that is equal to or greater than your wall height. If there's no pattern repeat (0 inches), the effective strip height is just the wall height.
Room Height (inches) = 8 ft × 12 = 96 inches
Pattern Repeat = 24 inches
Effective Strip Height = Ceiling(Room Height / Pattern Repeat) × Pattern Repeat
Effective Strip Height = Ceiling(96 / 24) × 24 = Ceiling(4) × 24 = 4 × 24 = 96 inches
In this example, the wall height is a perfect multiple of the pattern repeat, so the effective strip height is the same as the wall height. If the wall height was, say, 90 inches, the calculation would be Ceiling(90 / 24) × 24 = Ceiling(3.75) × 24 = 4 × 24 = 96 inches, meaning each strip would need to be 96 inches long to ensure pattern alignment.
6. Determine Strips Per Roll
Now, figure out how many of these "effective" strips you can get from a single roll of wallpaper.
Roll Length (inches) = 33 ft × 12 = 396 inches
Strips Per Roll = Floor(Roll Length / Effective Strip Height)
Strips Per Roll = Floor(396 inches / 96 inches) = Floor(4.125) = 4 strips per roll
7. Calculate Total Rolls Needed
Divide the total number of strips required by the number of strips you can get from each roll. Then, add a waste factor (typically 10-15%) to account for trimming, mistakes, and future repairs, and round up to the nearest whole roll.
Calculated Rolls = Total Strips / Strips Per Roll
Calculated Rolls = 26 / 4 = 6.5 rolls
Final Rolls (with 10% waste) = Ceiling(6.5 × 1.10) = Ceiling(7.15) = 8 rolls
Important Considerations
- Buy an Extra Roll: It's always a good idea to purchase one extra roll beyond your calculated amount. This provides a buffer for errors, future repairs, or if a specific dye lot becomes unavailable.
- Check Dye Lots: When buying multiple rolls, ensure they all have the same dye lot number. Slight color variations can occur between different production batches.
- Complex Rooms: Rooms with many angles, alcoves, or very high ceilings might require a professional estimate.
- Wallpaper Type: Some wallpapers (like grasscloth or murals) have unique installation requirements that might affect quantity.
Using this calculator and understanding the process will help you confidently purchase the right amount of wallpaper for a beautiful finish!