How to Use This Wallpaper Calculator
Enter your room's width, length, and wall height. Then add your wallpaper roll's width and length — find these on the roll's label or product listing. Set the pattern repeat to match your chosen wallpaper (leave at 0 for plain or texture patterns). Add any doors or windows as cutouts to subtract that area. Hit "Calculate" to get your roll count instantly.
Why This Matters
Buying too few rolls is a costly mistake — dye lots change between production runs, and even rolls with the same code can have subtle colour differences. If you run short mid-project, you may not be able to find an exact match. On the other hand, buying far too many wastes money. A typical 12×14 ft room with 8 ft ceilings needs about 8–10 single rolls, but that figure changes dramatically with a 24-inch pattern repeat (add 15–20% more) or a feature wall-only approach.
Interior designers routinely recommend ordering 10–15% extra for straight patterns and 15–20% for large pattern repeats. For rooms with many windows and doors — like a kitchen — cutouts can reduce your total by 1–2 rolls. Getting this math right before you order saves a trip to the store and guarantees a seamless installation.
How It's Calculated
Step 1 — Perimeter area: Total Wall Area = 2 × (Width + Length) × Height
Step 2 — Cutout area: Subtract door and window areas. A standard door ≈ 20 sq ft; a window ≈ 9–15 sq ft.
Step 3 — Strip length with pattern: Each strip needs Height + Pattern Repeat to allow matching.
Step 4 — Strips per roll: floor(Roll Length ÷ Strip Length)
Step 5 — Total strips needed: ceil(Net Wall Width ÷ Roll Width) per wall, summed.
Step 6 — Rolls needed: ceil(Total Strips ÷ Strips per Roll), then apply waste factor and round up.
Tips & Common Mistakes
- Always round up. Wallpaper is sold in whole rolls — never buy half a roll's worth and expect to be fine.
- Match dye lots. Note the lot/batch number on every roll and buy them all at once. Even a slight colour shift is visible on a wall.
- Don't fully subtract doors. A door's strip still uses part of the roll above it. This calculator correctly counts partial strips rather than simply removing full strip areas.
- Textured and plain wallpapers often have a small "random match" repeat — enter 0 unless the label states otherwise.
- Feature walls only? Enter just that wall's width and length instead of the full room to get an accurate single-wall estimate.
Frequently Asked Questions
How many rolls does a standard bedroom need?
A 12×12 ft bedroom with 8 ft ceilings typically needs 8–10 single rolls (American standard: 20.5 in × 33 ft). Add 10% for a plain pattern or 15–20% for a large pattern repeat. This calculator handles all of that automatically.
What is a "single roll" vs a "double roll"?
In the US, wallpaper is sold in double rolls (about 57–60 sq ft) but priced and listed per single roll (28–30 sq ft). Always confirm whether a listing is per single or double roll. Enter the actual length of the roll you're buying — if it's 66 ft, enter 66.
Why does pattern repeat matter so much?
With a 24-inch pattern repeat, every strip must be cut to start at the same point in the pattern. That means up to 24 inches of each strip is wasted at the bottom. On an 8 ft wall, this can reduce strips per roll from 4 to 3 — a 25% increase in rolls needed.
Should I include the ceiling in my calculation?
Standard wallpaper calculators — and this one — cover only the four walls. If you're papering the ceiling, measure it separately (width × length) and add that area. Run the calculation twice and add the roll counts together.