Wallpaper Calculator (Metric)
Enter your wall dimensions, doors, windows, and roll coverage to get the rolls of wallpaper you need.
What your result means
Rolls is what you buy, rounded up to whole double rolls. Adjusted area is your wall area minus doors and windows, plus waste for pattern matching. Buy a little over and keep the leftover roll for repairs.
How to use this calculator
- Measure the perimeter (add all wall lengths) and the wall height.
- Count doors and windows (we subtract standard sizes).
- Check your wallpaper roll spec - typical double roll covers 5.2 m².
- Use 15% waste for pattern-matched paper.
- Read rolls needed (rounded up).
The formula
Wall area is perimeter times height. Subtract 2 m² per door and 15 per window for the net area, add your waste percentage for pattern matching, then divide by the roll's coverage and round up.
Worked example
Say you've got a 12 by 3 m room (13.4 m around) with 2.4 m walls, 1 door, and 2 windows, using 5.2 m² rolls. Enter 44, 8, 1, 2, 56, and 15. You'll get 32.7 m² gross, 301 net after the openings, 346 with waste, and 7 rolls to buy.
Wallpaper waste by pattern repeat
| Pattern | Repeat | Waste to add |
|---|---|---|
| Plain / random match | None | 10% |
| Small repeat | Up to 15.2 cm | 15% |
| Large repeat | Over 30.5 cm | 20 – 25% |
Tips & gotchas
- A standard double roll covers 5.2 m² usable. Single rolls (2.6 m²) are rare in the US.
- Pattern repeat adds 15-25% waste, and the bigger the repeat the more you lose.
- Order from one dye lot, since color shifts between batches.
- Skip regular paper on bathroom ceilings and steamy rooms; use vinyl-coated there.
- Keep the leftover roll and the dye-lot number for repairs.
Frequently asked questions
How many rolls of wallpaper do I need?
Run the numbers above. Most rooms land at 5 to 10 double rolls.
What is pattern repeat?
The vertical distance before the design starts over. A bigger repeat wastes more paper.
Do I need to subtract doors and windows?
Yes, and the calculator does it for you: 2 m² per door and 15 per window.
Can I paper over existing wallpaper?
Yes, if the old paper is stuck down firmly. If it's lifting, strip it first.
How much does wallpaper installation cost?
Around $3 to $7 per square foot for labor, on top of the paper itself.
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