How this wallpaper roll calculator works
This is the standard strip method used by wallpaper retailers' own calculators: total wall width ÷ roll width gives the number of strips; wall height plus a fixed trim allowance (100mm, about 4 inches, for top and bottom slack) gives the length of one strip, rounded up to the next full pattern repeat if you set one; how many of those strips fit in one roll (rounded down) gives strips per roll; strips needed ÷ strips per roll, rounded up, gives rolls before any buffer. Each door or window then removes a flat width credit (700mm / 27.5in per opening) from the paperable wall width before the strip count is worked out — a conservative floor that only credits whole strips an opening fully covers, never a fractional strip. The waste buffer you choose is applied last and is always rounded up to a whole roll, never a fraction of one.
Sources
Strip-method formula (perimeter ÷ roll width = strips; height + trim = strip length; strips × strip length ÷ roll length = rolls) and the 10% plain-pattern / 15–20% large-repeat waste guidance: Wallcover, "Wallpaper Roll Calculator: How Many Rolls Do You Need?". Standard European roll size (0.53m × 10m): the same source. US "single roll" vs. double-roll bolt naming: US Wall Decor, "Single Roll vs Double Roll Wallpaper" and Wallpaper Boulevard, "Single vs Double Roll". Coverage and trim allowances vary by manufacturer — always check the figures printed on your roll's label. Verified against this calculator on September 18, 2026.
Questions
How many rolls of wallpaper do I need for a room?
Add up the width of every wall you're papering, divide by the roll width to get the number of strips, then divide the strips by how many strip-lengths fit in one roll (your ceiling height plus a trim allowance). Round each step up to a whole strip and a whole roll — you can't buy a fraction of either.
What's the difference between a "single roll" and a "double roll"?
In the US, wallpaper is usually shipped as a bolt about 33 feet long — physically two old-style single rolls joined together — but many retailers still price and list it per "single roll," even though what arrives is one double-roll bolt. Always check the roll dimensions printed on the label rather than assuming from the name.
How much extra wallpaper should I buy for waste?
About 10% is standard for a plain or small-pattern wallpaper. A large pattern repeat pushes real-world waste higher because more of each strip gets trimmed to keep the pattern aligned, so 15–20% is a more realistic buffer once the repeat is over about 25–26cm (10in).
Does a pattern repeat change how much wallpaper I need?
Yes. Every strip has to be cut long enough to land on a full repeat, so the strip length gets rounded up to the next multiple of the repeat — which can also reduce how many strips fit in one roll. A 640mm repeat on a 2.4m wall, for example, rounds a 2.5m strip up to 2.56m.
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