Wallpaper Calculator
Add up your wall dimensions and get the number of wallpaper rolls to order, with an allowance for the pattern repeat and trimming waste.
How it works
First we find the area you're covering: add up the width of every wall and multiply by the ceiling height. Forty feet of wall at 9 feet high is 360 square feet of surface to paper.
Then comes the allowance. Every time you hang a patterned strip you trim some off the top or bottom to line the design up with the strip beside it, and that offcut is wasted. A 15 percent allowance covers a typical repeat plus edge trimming.
Rolls are sold by coverage — an American double roll runs around 56 square feet of usable paper. We take the wall area, pad it by your allowance, divide by the roll coverage, and round up to whole rolls.
Frequently asked questions
Why not just divide wall area by roll coverage?
Because a patterned wallpaper wastes paper at every seam. If the design repeats every 21 inches, you can lose most of a repeat lining up each strip. The allowance is what turns a raw area into a realistic roll count.
What allowance should I use for a big pattern repeat?
The larger the repeat, the more you waste matching it. Plain or random-match papers can sit near 10 percent, standard repeats around 15, and a bold large-scale repeat can justify 20 to 25 percent.
Do I count doors and windows?
This tool uses your full wall area, which is the safe way to buy — the offcuts around openings often can't be reused because of the pattern match. If you want to trim the estimate, subtract large openings from your total width times height first.