How this wallpaper calculator works
Wallpaper is sold by the roll, so the job is to work out how many rolls cover your walls. A simple area estimate — wall area ÷ roll coverage — is a rough guide, but it ignores how wallpaper is actually hung: in full-height vertical strips, where leftover lengths from a roll usually cannot be reused. The accurate approach is strip-based.
First, work out how many strips you can cut from one roll: strips per roll = roll length ÷ (wall height + pattern repeat), rounded down, because each strip must be cut to a whole multiple of the repeat so adjacent strips line up. Then work out how many strips it takes to cover the walls: strips needed = total wall width ÷ roll width, rounded up. Finally, rolls = strips needed ÷ strips per roll, rounded up. Add a waste allowance of 10–15% for trimming, mistakes and damage. If you leave the pattern repeat at zero, the tool falls back to a straight area-based estimate instead.
Reference note: results are a planning estimate. Pattern repeat type (straight vs offset/drop match), the number and size of openings, ceiling height variations and how much you can salvage from offcuts all change real usage. Measure carefully, add a sensible waste allowance, and confirm coverage on the roll label before buying.
Frequently asked questions
- How many rolls of wallpaper do I need?
- Work out how many full-height strips you can cut from one roll, then how many strips it takes to go around your walls. Strips per roll is the roll length divided by the wall height plus the pattern repeat, rounded down. Strips needed is the total wall width divided by the roll width, rounded up. Divide the strips you need by the strips per roll and round up to get the rolls. Enter your wall and roll dimensions above and the calculator returns the count.
- How does pattern repeat affect how many rolls I need?
- A pattern repeat is the vertical distance before the design starts again. To make adjacent strips line up, each strip is cut to the next whole multiple of the repeat, so wallpaper is trimmed off the top of every strip. A larger repeat wastes more per strip, which means fewer usable strips per roll and more rolls overall. The calculator adds the repeat to each strip length so the estimate stays realistic.
- How much extra wallpaper should I buy?
- About 10 to 15 percent is standard, on top of any pattern repeat already accounted for. The strip-based method already wastes part of each roll because a roll rarely divides evenly into whole strips, but the extra percentage covers trimming, mistakes and damage. Always buy a little more than the bare minimum, and keep a spare roll from the same batch so the colour matches for future repairs.
- How do I measure my walls for wallpaper?
- Measure the total width to be papered — add up the width of every wall, or use the room perimeter — and the wall height from skirting to ceiling. Or enter the room length, width and height and the calculator works out the perimeter and wall area for you. Measure in the same unit, or let the calculator convert feet and inches or metres and centimetres.
- Should I subtract doors and windows?
- For most rooms it is safest not to subtract small doors and windows. A strip running past an opening still comes from a full-height drop, and the offcut rarely yields a usable piece elsewhere. Only deduct very large openings such as patio doors or a wall of glass. Leaving openings in keeps a margin for error and gives you offcuts and spares.
- What is a standard roll size?
- The most common is the European roll at about 0.53 m wide and 10 m long, covering roughly 5 square metres. American rolls are wider — typically a double roll around 27 in wide by 27 ft long. Sizes vary by brand, so always check the label and enter the exact roll width and length, because those numbers drive how many strips you get per roll.