";detail+="Strips Required: "+stripsNeeded+"
";detail+="Strips per Roll: "+stripsPerRoll+"
";detail+="Base Rolls: "+baseRolls+"
";detail+="Waste Factor applied: "+wastePct+"%";document.getElementById('detailBox').innerHTML=detail;}else{document.getElementById('detailBox').innerHTML="";}}
Using the Wallpaper Calculator
Whether you are renovating a single accent wall or an entire home, using a wallpaper calculator is the most critical step in your project planning. This tool helps you estimate the exact number of rolls required while accounting for pattern repeats, waste, and architectural features like doors and windows.
To get started, measure the height and total width of all walls you intend to cover. If you have multiple walls with different heights, calculate them separately or use the average height for a quick estimate.
- Wall Height & Width
- Measure from the top of the baseboard to the bottom of the ceiling molding. Width should be the total horizontal distance of all walls.
- Roll Width & Length
- Standard American rolls are often 20.5 inches or 27 inches wide. European (Metric) rolls are typically 52cm or 53cm wide. Check the product label for length, usually 33 feet (10 meters) for a double roll.
- Pattern Repeat
- The vertical distance between where a pattern starts and where it repeats. This is vital because you must align the pattern between strips, leading to significant waste.
How the Calculation Works
The wallpaper calculator uses the "Strip Method" which is the industry standard for professional installers. Unlike a simple area calculation, the strip method ensures you have enough length to match patterns vertically across the wall.
Total Rolls = ceil( (Total Width / Roll Width) / floor( Roll Length / (Wall Height + Pattern Adjustment) ) ) * (1 + Waste Factor)
- Strips Needed: How many vertical pieces of wallpaper are required to cover the horizontal width.
- Usable Strip Length: The wall height plus any additional length needed to align the pattern repeat.
- Strips per Roll: How many full-height pieces can be cut from a single continuous roll.
- Waste Factor: An additional 10-15% buffer for cutting errors, mistakes, or future repairs.
Calculation Example
Scenario: You are wallpapering a room with a total wall width of 40 feet and a height of 8 feet. You chose a roll that is 20.5 inches wide and 33 feet long with a 20-inch pattern repeat.
Step-by-step solution:
- Convert Units: Roll width 20.5″ = 1.708 ft.
- Strips Needed: 40 ft / 1.708 ft = 23.4 (Round up to 24 strips).
- Adjust for Repeat: Since the repeat is 20″, and the wall is 96″ (8ft), you need 5 full repeats (100″) per strip to align the pattern.
- Strips per Roll: 33 ft (396″) / 100″ = 3.96 (Only 3 full strips per roll).
- Base Rolls: 24 strips / 3 strips per roll = 8 rolls.
- Final Result: Adding 10% waste (0.8 rolls), you should purchase 9 rolls.
Common Wallpaper Questions
Should I subtract windows and doors?
If you have a very large sliding glass door or multiple large windows, you can subtract their area (e.g., 20 sq ft for a standard door). However, most pros recommend not subtracting small windows, as the extra paper is useful for "wrapping" into the window frame or acting as a safety buffer.
What is a "Double Roll"?
Most wallpaper sold in the US is priced as a "single roll" but sold only as a "double roll" (one continuous bolt). Our wallpaper calculator uses the actual length of the bolt you are buying. Always verify if the length provided on the website or label is for a single or double roll before entering it into the calculator.
How much extra should I buy?
A waste factor of 10% is standard for plain or small patterns. For large geometric patterns or "drop matches," increase your waste factor to 15-20%. It is always better to have one roll left over than to run out and find that the manufacturer's "dye lot" has changed, resulting in a slight color mismatch.