Wallpaper Calculator
Calculate exactly how many rolls of wallpaper you need based on room size, roll dimensions, pattern repeat, and waste allowance. Perfect for DIY decorating projects.
How to Calculate How Much Wallpaper You Need
Calculating wallpaper quantities involves more than just measuring wall area. Here's the complete formula this calculator uses:
- Calculate room perimeter: Add the length and width of the room together and multiply by 2[reference:5].
- Calculate total wall area: Multiply the perimeter by the ceiling height[reference:6].
- Subtract openings: Subtract the area of doors (~20 sq ft each) and windows (~12 sq ft each)[reference:7].
- Calculate roll coverage: Multiply roll width by roll length to get total square footage per roll[reference:8].
- Adjust for pattern repeat: Larger pattern repeats reduce usable yield — see the guide above[reference:9].
- Add waste allowance: Add 10-20% for cutting, matching, and mistakes[reference:10].
Example: A 12ft × 15ft room with 8ft ceilings has a perimeter of 54ft and a wall area of 432 sq ft. Subtract 60 sq ft for 1 door and 2 windows (372 sq ft net). With a standard roll covering 56 sq ft and a 15% waste allowance, you'd need about 8 rolls[reference:11].
Why Use This Wallpaper Calculator?
- Avoid buying too much or too little: Get the exact number of rolls needed.
- Account for pattern repeats: Larger patterns need more wallpaper — this calculator handles it.
- Save money: Buy only what you need, plus a spare roll for future repairs.
- Plan your project: Know exactly how much wallpaper to order before you start.
Important Tips for Buying Wallpaper
- Buy from the same lot/batch: Wallpaper colors can vary between batches — always check the run number[reference:12].
- Buy an extra roll: Keep one for future repairs or in case of mistakes during installation[reference:13].
- Check return policies: Most stores accept returns of unopened rolls within 30-90 days[reference:14].
- Order samples first: Test the wallpaper in your space before buying in bulk[reference:15].
How Accurate Is This Calculator?
This calculator uses industry-standard formulas recommended by Sherwin-Williams, Bankrate, and professional decorators[reference:16][reference:17]. Results are accurate to within 1 roll for most rooms. For complex spaces with sloped ceilings, alcoves, or unusual shapes, we recommend consulting a professional decorator.
Frequently Asked Questions
Measure the perimeter of the room (sum of all wall lengths) and multiply by the ceiling height to get the total wall area. Subtract the area of doors and windows. Then divide by the usable coverage per roll (which depends on pattern repeat). Add 10-20% waste allowance. This calculator does all the math for you.
Standard wallpaper rolls are typically 20.5 inches wide and 33 feet long (52 cm × 10 m), covering about 56 square feet (5.2 m²)[reference:18]. US double rolls are 20.5″ × 66′ covering about 112 sq ft[reference:19]. European metric rolls are 0.53m × 10m covering about 5.3 m²[reference:20].
Pattern repeat is the vertical distance between identical pattern elements. Larger pattern repeats create more waste because each strip must be cut to match the pattern[reference:21]. For 0-6 inch repeats, waste is minimal. For 6-12 inch repeats, add 10-15% waste. For repeats over 12 inches, add 15-25% waste[reference:22].
It's recommended to buy 1-2 extra rolls for mistakes, future repairs, or matching issues[reference:23]. Also, always buy wallpaper from the same batch/lot number to ensure colour consistency across all rolls[reference:24].
Yes, subtract the area of doors and windows from the total wall area. A standard door is about 20 sq ft, a standard window about 10-15 sq ft[reference:25]. This calculator lets you enter the number of doors and windows for accurate estimates.
A single roll is 20.5″ wide × 33′ long (≈56 sq ft). A double roll is 20.5″ wide × 66′ long (≈112 sq ft)[reference:26]. Wallpaper is often priced by the single roll but sold in double rolls — always check what you're ordering[reference:27].