how to calculate how much wallpaper is needed

How to Calculate How Much Wallpaper is Needed: A Comprehensive Guide

Embarking on a wallpapering project can transform a room, adding character, warmth, or a bold statement. However, one of the most common pitfalls is miscalculating the amount of wallpaper needed. Too little, and you're left scrambling for more, possibly facing dye-lot differences. Too much, and you've wasted money. This guide, along with our handy calculator, will help you get it right the first time.

Why Accurate Measurement Matters

• Cost-Efficiency: Avoid overspending on excess rolls or incurring extra shipping costs for forgotten ones.
• Consistency: Ensure all rolls come from the same dye lot to prevent subtle color variations that can ruin your finish.
• Time-Saving: Prevent delays in your project due to re-ordering or searching for matching rolls.
• Professional Finish: Proper planning contributes to a smoother, stress-free installation process.

What You'll Need Before You Start

Gather these essential tools for precise measurements:

• Measuring tape (preferably a long, retractable one)
• Pencil and paper
• A calculator (or use our integrated tool above!)
• A stepladder or stool for reaching high spots

Step-by-Step Wallpaper Calculation

Follow these steps to determine the exact amount of wallpaper for your project.

1. Measure Your Room Dimensions

The first and most critical step is to accurately measure the room you plan to wallpaper.

1. Room Length: Measure the length of each wall. If your room is rectangular, you'll have two pairs of equal lengths.
2. Room Width: Measure the width of the room. Again, you'll have two pairs of equal widths.
3. Room Height: Measure the height from the floor to the ceiling. Take several measurements around the room, as ceilings and floors can be uneven. Use the greatest height measurement to ensure you have enough paper.

For example, if your room is 12 feet long, 10 feet wide, and 8 feet high.

2. Calculate the Room's Perimeter

The perimeter is the total distance around the room. Add the lengths of all the walls together.

Perimeter = (2 x Room Length) + (2 x Room Width)

Using our example: (2 x 12 ft) + (2 x 10 ft) = 24 ft + 20 ft = 44 feet.

3. Calculate the Total Wall Area

Multiply the room's perimeter by the height to get the total square footage of the walls.

Total Wall Area = Perimeter x Room Height

Using our example: 44 ft x 8 ft = 352 square feet.

4. Measure and Calculate Obstacle Areas (Doors & Windows)

You won't be wallpapering over doors and windows, so you need to subtract their areas from the total wall area. Measure the height and width of each door and window.

1. Door Area: Door Width x Door Height. If you have multiple doors of the same size, multiply this by the number of doors.
2. Window Area: Window Width x Window Height. Similarly, multiply by the number of windows if they are identical.

For example, one door (2.5 ft wide x 6.5 ft high = 16.25 sq ft) and two windows (each 3 ft wide x 4 ft high = 12 sq ft, so 2 x 12 = 24 sq ft).

Total Obstacle Area = Total Door Area + Total Window Area

Using our example: 16.25 sq ft + 24 sq ft = 40.25 square feet.

5. Determine the Wallpaperable Area

Subtract the total obstacle area from the total wall area.

Wallpaperable Area = Total Wall Area - Total Obstacle Area

Using our example: 352 sq ft - 40.25 sq ft = 311.75 square feet.

6. Understand Wallpaper Roll Dimensions

Wallpaper rolls come in various sizes, but a common "standard double roll" in the US is approximately 20.5 inches wide and 33 feet long.

• Width: 20.5 inches (or 1.708 feet)
• Length: 33 feet

7. Calculate Area Per Roll

Multiply the width by the length of a single roll to find its total square footage.

Area Per Roll = Roll Width (in feet) x Roll Length (in feet)

For a standard double roll: 1.708 ft x 33 ft = 56.364 square feet (approximately 56.375 sq ft for the calculator).

8. Divide Wallpaperable Area by Roll Area

Now, divide the wallpaperable area by the area of one roll.

Rolls Needed (before waste) = Wallpaperable Area / Area Per Roll

Using our example: 311.75 sq ft / 56.375 sq ft/roll = 5.53 rolls.

9. Account for Waste (Pattern Match & Trimming)

This is a crucial step often overlooked! You'll need extra wallpaper for:

• Pattern Repeat: If your wallpaper has a repeating pattern, you'll need to align the design, which means cutting off excess at the top and bottom of each strip. The larger the pattern repeat, the more waste you'll generate.
• Trimming: You'll trim excess paper at the ceiling, floor, and around obstacles.
• Mistakes: Accidents happen! It's always good to have a little buffer.

A general rule of thumb is to add 10-20% for waste. For simple patterns or plain paper, 10% might suffice. For large, complex patterns, or if you're a beginner, aim for 15-20%.

Rolls Needed (after waste) = Rolls Needed (before waste) x (1 + Waste Factor as a decimal)

Using our example with a 10% waste factor (0.10): 5.53 rolls x (1 + 0.10) = 5.53 x 1.10 = 6.083 rolls.

10. Round Up to the Nearest Whole Roll

You cannot buy partial rolls. Always round up to the next whole number.

Using our example: 6.083 rolls rounds up to 7 rolls.

Tips for Accuracy and Best Practices

• Double-Check Your Measurements: Measure everything at least twice to avoid errors.
• Consider Pattern Repeat: If your wallpaper has a large pattern repeat, you might need more rolls than a plain paper. Manufacturers often provide guidance on this.
• Buy an Extra Roll: Even after careful calculations, it's wise to purchase one extra roll, especially for future repairs or if you underestimated. Just ensure it's from the same dye lot!
• Check Manufacturer's Specifications: Always refer to the wallpaper manufacturer's instructions for roll dimensions and any specific recommendations.
• Consider Wall Prep: Ensure your walls are smooth and properly primed for the best adhesion and finish.

Conclusion

Calculating the correct amount of wallpaper is a foundational step for a successful DIY project. By following these steps and utilizing our calculator, you can approach your wallpapering task with confidence, ensuring you have just the right amount of material to transform your space beautifully. Happy decorating!