Wallpaper Calculator: 20 × 20 ft room
Estimate how many rolls of wallpaper a room needs, with doors and windows removed and pattern-repeat waste included.
// Bill of materials
Costs are rough, materials only — edit the price to match your quote.
Pre-filled for a 20 × 20 ft room. Change any value to recalculate, or start from scratch.
How it's calculated
Wall area = perimeter × height = 2 × (width + length) × ceiling height. We subtract 21 sq ft per door and 15 sq ft per window, add waste for the pattern repeat, then divide by the usable coverage of one roll and round up.
Worked example — 20 × 20 ft room
- Room width
- 20 ft
- Room length
- 20 ft
- Ceiling height
- 8 ft
- Doors
- 1 count
- Windows
- 2 count
- Roll type
- Double roll (~56 usable sq ft)
- Waste (pattern repeat)
- 15 %
- Price per roll
- 30 $
Nearby sizes
| Room size | Rolls to buy | |
|---|---|---|
| 8 × 8 ft room | 5 rolls | Open |
| 8 × 10 ft room | 5 rolls | Open |
| 8 × 12 ft room | 6 rolls | Open |
| 10 × 10 ft room | 6 rolls | Open |
| 10 × 12 ft room | 7 rolls | Open |
| 10 × 14 ft room | 7 rolls | Open |
| 10 × 16 ft room | 8 rolls | Open |
| 12 × 12 ft room | 7 rolls | Open |
| 12 × 14 ft room | 8 rolls | Open |
| 12 × 16 ft room | 9 rolls | Open |
| 12 × 18 ft room | 9 rolls | Open |
| 20 × 20 ft room (this page) | 13 rolls |
Tips for buying wallpaper
- Buy all rolls from the same batch (check the run number) — shades drift between production runs.
- A large pattern repeat wastes more; go 20–30% waste for big repeats, 10–15% for small ones.
- Order one extra roll beyond the estimate for future repairs and mistakes on tricky walls.
- Usable coverage is less than the roll's total because of trimming and pattern matching — we already account for that.
- Measure and hang around windows and doors carefully; those cuts eat material fast.
- Prep and prime the wall first; wallpaper telegraphs every bump underneath it.
Frequently asked questions
How many rolls of wallpaper do I need for a 12x14 room?
With 8 ft ceilings, a door and two windows, and a double roll, a 12×14 room needs about 8 rolls including pattern waste. Bigger repeats need more.
Why is usable coverage less than the roll size?
You lose material trimming the top and bottom and matching the pattern between strips. We estimate usable coverage per roll, not the paper's total area.
How much extra for pattern repeat?
Small repeats waste about 10–15%; large repeats 20–30%. Set the waste field to match your paper's repeat.
Should I subtract doors and windows?
Yes. We remove 21 sq ft per door and 15 sq ft per window. Adjust the counts to match your room.