Wallpaper calculator — wall area to rolls to buy
Enter wall area, subtract doors and windows, add pattern waste, and divide by the coverage printed on your roll. Switch imperial or metric anytime and round up to whole rolls before you shop.
Results
Net area: 360 sq ft
With waste: 414 sq ft
Rolls to buy: 14
Formula
net=wall−openings; withWaste=net×(1+waste); rolls=ceil(withWaste÷coverage)
How the numbers are calculated
- Net area = 400 − 40 = 360 sq ft
- Rolls to buy = ceil(414 ÷ 30) = 14
Running one roll short halfway around a room is a special kind of pain: dye lots change, and the store may not have the same batch. Over-buying a little with a clear waste percent is cheaper than an emergency second trip.
Start from measured wall area, subtract openings you will not cover, then multiply by waste for pattern matching and awkward cuts. Divide by the coverage on the roll you actually intend to buy — marketing “room size” charts on tags are often optimistic.
Keep one spare roll from the same dye lot for future repairs. If the wall is still bare drywall that needs sheets first, estimate those with drywall sheets before paper goes up.
How to use
- Enter wall area and door/window openings
- Set pattern waste % and coverage per roll
- Read net area, area with waste, and rolls to buy
Why this calculator
- Subtracts doors and windows instead of papering empty air
- Builds pattern waste into the buy count
- Switches imperial and metric without rewriting the room
Good for
- Accent walls
- Full-room refreshes
- Rental-friendly updates
Tips
- Buy every roll from one dye lot when you can.
- Keep a spare roll for repairs years later.
- Bump waste for large repeats or many corners.
Examples
| Input | Output | Note |
|---|---|---|
| 400 sq ft walls, 40 sq ft openings, 15% waste, 30 sq ft per roll | 14 rolls | Net 360 → with waste 414 → ceil(414÷30)=14 |
| One accent wall 12×8 ft, small window 3×4 ft, 10% waste, 28 sq ft/roll | About 4 rolls | Measure the wall you will cover, not the whole room, for accent jobs |
Wallpaper FAQ
- How much waste should I leave?
- Large repeats often need 10–20%. Straight matches and solids can sit nearer 5–10%. When the label lists coverage, prefer that number over store “room charts.”
- Do I include the ceiling?
- Only if you are papering it. Most wall jobs leave the ceiling out of wall area and openings.
- Painting instead?
- Use Paint calculator for cans; come back here when you switch to vinyl or paper.
- Why buy from one dye lot?
- Batches shift under daylight. An emergency roll from another lot can look half a shade off on a long wall.