how to calculate how much wallpaper you need

Embarking on a wallpaper project can transform a room, adding character, texture, and depth. However, one of the most common pitfalls is miscalculating how much wallpaper to buy. Too little, and you face delays and potential color batch differences; too much, and you've wasted money. This guide, along with our handy calculator, will ensure you get it right the first time.

The Basic Formula for Wallpaper Calculation

At its core, calculating wallpaper involves finding the total surface area of your walls, subtracting any areas that won't be papered (like windows and doors), and then adding a little extra for waste and pattern matching. Here's the general idea:

(Room Perimeter × Room Height) - Total Obstacle Area + Waste Factor = Total Wallpaperable Area

Once you have the total wallpaperable area, you divide it by the coverage area of a single roll of wallpaper to find out how many rolls you need.

Step-by-Step Guide to Measuring Your Room

1. Measure Your Room Dimensions

Accuracy is key here. Grab a tape measure, a notepad, and a pencil.

• Room Length: Measure the length of each wall. If your room is rectangular, you'll have two pairs of equal lengths.
• Room Width: Measure the width of the room. Again, you'll have two pairs of equal widths.
• Room Height: Measure the height from the floor to the ceiling. Do this in several places around the room, as floors and ceilings can sometimes be uneven. Use the greatest height measurement to be safe.

For our calculator, you will input the length, width, and height once. The calculator will then determine the total perimeter and multiply by height to get the initial wall area.

2. Account for Doors and Windows (Obstacle Area)

You don't want to wallpaper over your doors and windows, so these areas need to be subtracted from your total wall area.

• Measure Each Obstacle: For every door, window, or other significant opening, measure its width and height.
• Calculate Individual Areas: Multiply the width by the height for each obstacle to get its individual square footage.
• Sum Them Up: Add all these individual obstacle areas together to get your "Total Obstacle Area." This is the value you'll input into the calculator.

3. Factor in Waste and Pattern Repeat

This is a crucial step that many DIYers overlook, leading to shortages. Wallpaper comes with a pattern repeat, meaning you'll need to align the pattern from one strip to the next. This often requires cutting off excess at the top and bottom of each strip to match the design.

• Pattern Repeat: The larger the pattern repeat, the more waste you'll likely have. This information is usually found on the wallpaper roll label.
• General Waste Factor: We recommend adding a 15% waste factor to your total calculated area. This accounts for pattern matching, trimming, and any minor mistakes during installation. Our calculator automatically adds this percentage.

Using the Wallpaper Roll Calculator

Our calculator simplifies the process by taking your raw measurements and providing an estimated number of rolls. Here's how to use it:

1. Measure: Follow the steps above to measure your room's length, width, and height, and calculate the total area of all doors and windows.
2. Input: Enter these values into the respective fields in the calculator above.
3. Calculate: Click the "Calculate Rolls" button.
4. Result: The calculator will display the estimated number of standard wallpaper rolls you need, accounting for a 15% waste factor.

Understanding Wallpaper Roll Sizes

It's important to note that "standard" wallpaper roll sizes can vary slightly by region and manufacturer. For the purpose of this calculator, we assume a common North American double roll size which covers approximately 56 square feet (e.g., 33 feet long by 1.7 feet wide). Always double-check the coverage area specified on your chosen wallpaper's product description or label, as European rolls often differ (e.g., 10 meters long x 0.53 meters wide, covering 5.3 square meters).

If your chosen wallpaper has a significantly different coverage area, you might need to adjust manually or use the calculator's output as a close estimate and then fine-tune based on the actual roll size.

Tips for Buying and Applying Wallpaper

• Buy an Extra Roll: Even with careful calculation, it's always a good idea to buy one extra roll, especially if it's a specialty or limited-run design. You can often return unopened rolls.
• Check Dye Lots: When purchasing multiple rolls, ensure they all come from the same "dye lot" or "batch number." This guarantees consistent color and pattern between rolls.
• Prepare Your Walls: For the best results, ensure your walls are clean, smooth, and primed before wallpapering.
• Consider Professional Help: If you're tackling a complex pattern or a particularly challenging room, don't hesitate to consult a professional wallpaper hanger.

With accurate measurements and a little planning, your wallpaper project will be a smooth success, leaving you with a beautifully transformed space.