Wallpaper Calculator
Order the right number of wallpaper rolls the first time. Accounts for roll size, pattern repeat, and doors and windows, by working out how many full-height strips each roll gives you.
Rolls to buy
How to calculate wallpaper
- Add up the width of every wall you will paper and measure the height.
- Enter the roll width and length from the label (US double rolls are often 20.5 in × 33 ft) and the pattern repeat.
- Enter doors and windows. Each saves part of a strip, and the calculator allows for that conservatively.
Why strips matter more than square feet
Dividing wall area by roll coverage underestimates wallpaper, because every strip has to be cut to full height plus the pattern repeat, and the offcut at the end of a roll is often too short to use. This calculator works the way installers do: it finds how many full-height strips fit on each roll and how many strips cover the walls.
Each strip is the wall height plus one pattern repeat (to line the pattern up) plus a few inches for trimming. Doors and windows reduce the number of full strips needed, but the short pieces above and below them still use paper, so they are counted at a reduced rate.
Buy all rolls from the same batch (lot) number so colors match, and get one extra roll for future repairs. Patterned papers with large repeats can need 15–25% more than plain ones.
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Frequently asked questions
How many rolls of wallpaper do I need for a 12×12 room?
With 8 ft walls, a standard 20.5 in × 33 ft roll and a 21 in repeat, roughly 9–10 rolls (about 3 strips per roll), depending on doors and windows.
What is a pattern repeat?
The vertical distance before the pattern repeats. Each strip needs extra length so the pattern lines up with the next.
What is a double roll?
Most US wallpaper is sold in double rolls (about 56 sq ft). Some brands price single rolls but package doubles.
Should I buy extra?
Yes, at least one roll from the same batch for mistakes and future repairs.