Why we count strips, not square feet
Wallpaper goes up in vertical strips, one roll width at a time. A 33-foot roll doesn't give you 33 feet of usable paper on an 8-foot wall. It gives you four full strips, and the 1-foot offcut is too short for anything except the spot above a door.
So the calculator does three things. It finds how many strips fit across your walls. It works out how many full strips one roll can give you. Then it divides the first number by the second and rounds up.
Worked example: 40 feet of wall, 8 feet high
- Strips needed: 40 ft × 12 = 480 in, ÷ 20.5 in = 24 strips
- No pattern repeat, so each 33 ft roll gives 4 strips of 8 ft
- 24 ÷ 4 = 6 rolls
Now give it a 21-inch pattern repeat. Each strip has to be cut about 9.75 feet long so the pattern lines up, and a roll only yields 3 strips. The same room now needs 8 rolls.
Single rolls and double rolls
In the US, wallpaper is often priced per single roll but sold only in double rolls. A double roll is one continuous piece of about 56 square feet. Make sure the length you enter matches what you're buying. European rolls and peel-and-stick panels come in other sizes, so read the label.
Tips for a clean job
- Order every roll from the same batch number. Colors shift slightly between print runs.
- Don't subtract doors and windows unless they're very wide. The paper around them still comes from full strips.
- Drop-match patterns use more paper than straight-match ones. Add one extra roll.
- Roll on a wallpaper primer first. Hanging is easier, and removal years later is far easier.
Painting the other walls? The paint calculator will tell you how much to buy.
Frequently asked questions
How many rolls of wallpaper do I need for a 12 by 12 room?
With 8-foot walls, 20.5 inch by 33 foot rolls and no pattern repeat, about 8 double rolls for all four walls. A large repeat can push that to 10.
What is a pattern repeat?
It's the vertical distance before the design starts over. A bigger repeat means more paper gets trimmed from each strip to line up the pattern with the strip beside it.
What is a drop match in wallpaper?
In a drop match, the pattern on each strip sits half a repeat lower than the strip next to it. It gives a diagonal look and usually needs a bit more paper.
How much extra wallpaper should I buy?
The strip method already covers most of the waste. Buy one extra roll for mistakes and future repairs, because the same batch can be hard to find later.
Results are estimates for planning. Product coverage, site conditions and installation methods vary, so check manufacturer guidance before you buy.