Work out how many rolls of wallpaper your room really needs, including the pattern repeat, doors, windows and a sensible waste allowance — before you order.
Wallpaper Calculator
How this wallpaper calculator works
The calculator first works out your net wall area, subtracting a standard door and window size for each opening you enter. It then thinks in strips, the way wallpaper is actually hung: each strip must cover your wall height, match the pattern repeat and allow a little trimming at the top and bottom. From your chosen roll size it counts how many usable strips each roll gives, rounds up, and finally adds your waste allowance. Order all rolls from the same batch so the colours match exactly.
Good to know
Plain wallpaper with no repeat hangs with little waste because each strip can start at the ceiling line. Patterns with a repeat must line up, so each strip needs extra length and you lose more at the top and bottom, especially with a large motif.
Keep one spare roll from the same batch for repairs and for matching around doors and windows, especially if the design may be discontinued. Paste choice matters too: paste-the-wall suits modern non-woven papers, while heavy vinyls and older papers usually need paste on the paper itself; ready-mixed adhesive grips heavy materials best.
Frequently asked questions
Q: Should I buy an extra roll? A: One spare roll is cheap insurance against a torn strip or a later repair, and unopened rolls can often be returned — check the shop’s policy.
Q: Does pattern repeat really matter? A: Yes. A large repeat forces each strip to start at the same point in the pattern, which shortens the usable length of every roll. Plain wallpapers with zero repeat are the most economical.
Q: Which paste should I use? A: Check the roll label first. Paste-the-wall suits many modern non-woven papers and lets you hang dry strips, while traditional papers often need paste applied to the backing; heavy vinyls grip best with ready-mixed adhesive.
Q: Can I wallpaper straight over old wallpaper? A: It is usually better to strip the old paper first so seams do not show and adhesion lasts. If the old layer is firmly stuck and smooth, test an area and use a suitable lining paper.