Wallpaper Calculator
Required Materials
What Is a Wallpaper Calculator?
A wallpaper calculator is a tool that converts room measurements into the number of wallpaper rolls you should order.
Unlike paint, wallpaper is installed in vertical strips called drops. Each drop must be cut to the right height, often with extra length for trimming and pattern matching. That is where many people make mistakes.
This calculator is built around the drop method, which is the standard method used by installers.
Why Square Footage Alone Does Not Work
Many online tools only ask for room size in square feet. That sounds easy, but it often leads to errors.
Here is why:
- Wallpaper is hung in vertical strips, not spread flat.
- Pattern repeats create waste that square footage ignores.
- Roll width matters just as much as roll length.
- Doors and windows reduce usage, but not in a simple way.
This calculator avoids those problems by working from wall width, wall height, and roll dimensions.
What This Wallpaper Calculator Does Differently
This calculator is designed to be practical and conservative. It aims to prevent under-ordering, which is the most expensive mistake with wallpaper.
Here is what it focuses on:
- Uses total wall width instead of room area
- Calculates full vertical drops
- Adds trim allowance for cutting
- Adjusts for pattern repeat
- Deducts doors and windows carefully
- Rounds up to full rolls only
The result is a number you can trust.
Inputs Explained in Plain Terms
Total Width of All Walls (Feet)
This is the combined length of every wall you plan to cover.
Example:
If the room has four walls that are each 10 feet wide, enter 40 feet.
Do not subtract doors or windows here. The calculator handles that later.
Room Height (Feet)
This is the floor-to-ceiling height.
Even if the ceiling is slightly uneven, measure the tallest point. Wallpaper must reach the highest spot.
Doors and Windows (Quantity)
Enter how many doors and windows are in the room.
Each opening is treated as a small deduction, but not a full subtraction. This reflects real-world installation, where wallpaper is still cut and trimmed around openings.
Roll Width (Inches)
Wallpaper comes in different widths. Common options include:
- 20.5 inches (standard in the US)
- 21 inches (common in Europe)
- 27 inches (commercial)
- 36 inches (grasscloth and specialty papers)
Wider rolls mean fewer drops, but they also change waste calculations.
Roll Length (Feet)
Most standard wallpaper rolls are 33 feet long. Some specialty papers vary, so this field is editable.
Pattern Repeat (Inches)
This is one of the most important inputs.
- Enter 0 for random or no-match patterns
- Enter the repeat size for patterned wallpaper (for example, 18 or 24 inches)
Larger repeats increase waste because each drop must align with the pattern above it.
How the Calculator Works (Step by Step)
This section explains the logic without code.
Step 1: Convert Height to Inches
The calculator converts room height from feet to inches and adds a small trim allowance. This extra length accounts for cutting at the top and bottom.
Step 2: Adjust for Pattern Repeat
If a pattern repeat is entered, the calculator rounds the drop height up to the nearest full repeat.
This ensures every strip aligns correctly.
Step 3: Calculate Total Drops Needed
Total wall width is converted to inches and divided by roll width.
The result is the number of vertical strips needed to cover the walls.
Step 4: Calculate Total Length Required
Each drop uses a fixed amount of wallpaper.
Total drops multiplied by drop height gives the total linear length needed.
Step 5: Account for Doors and Windows
Each door or window is treated as a small reduction in usage. The calculator applies this conservatively, so you still have enough material.
Step 6: Convert Length Into Rolls
Finally, the calculator divides the total length by roll length and rounds up to whole rolls.
You always order whole rolls. Partial rolls are not an option.
Understanding the Results
Rolls to Order
This is the number you care about most. It is rounded up and slightly conservative on purpose.
Ordering one extra roll is cheaper than stopping mid-job.
Total Drops (Strips)
This tells you how many vertical strips will be installed across the room. Installers often think in drops, so this number is useful when planning labor.
Usage Logic
This section explains how much wallpaper each drop uses and whether pattern repeat increases waste.
It helps you understand why the number of rolls is what it is.
Who Should Use This Calculator?
This wallpaper calculator is useful for:
- Homeowners planning a DIY wallpaper project
- Interior designers estimating materials
- Contractors preparing quotes
- Renters trying to avoid overbuying
It is especially helpful for patterned wallpaper, where mistakes are common.
Tips for Best Results
- Always measure twice
- Use the tallest wall height
- Enter pattern repeat exactly as listed on the roll
- When in doubt, order one extra roll
- Keep leftover rolls for future repairs
Wallpaper batches can vary slightly in color. Buying extra later may not match.