Wallpaper Strip Counter

Wallpaper strip calculation determines how many vertical strips are needed to cover a wall from baseboard to ceiling, and how many strips can be cut from one standard roll, accounting for pattern matching.

Strips per wall formula: Number of Strips = Wall Width (inches) ÷ Wallpaper Width (inches) Round up to the nearest whole number.

Strips per roll formula: Strips per Roll = Roll Length ÷ Strip Length, rounded DOWN

Rounding down is what handles end waste. A 396-inch roll cut into 130-inch strips gives 3 full strips and a 6-inch tail, and that tail is too short to hang. It is offcut, not a fourth strip.

Strip length (with pattern repeat): Strip Length = Ceiling Height + 4 in trim + Pattern Repeat Each new strip has to start at the right point in the pattern to line up with its neighbour, which is where the repeat allowance goes. The 4 inches is separate: it is the couple of inches top and bottom that you trim off against the ceiling line and the baseboard, and no wall is square enough to skip it.

Rolls needed: Rolls Needed = Total Strips Needed ÷ Strips per Roll Always round up, never down, then add about 10% on top as a safety buffer. For any job under ten rolls that works out to one extra roll, which is what most hangers buy anyway.

What each variable means:

• Wallpaper width: standard rolls run 20.5–27 inches wide in the US, 53 cm in Europe
• Roll length: the common US bolt is 33 feet (396 inches). A European bolt is 10 meters (393 inches), so the two are near enough the same length and differ mainly in width.
• Pattern repeat: the vertical distance before the design repeats. Random-match or straight-match patterns waste less. Drop-match patterns, where alternate strips are offset, waste more.
  • No repeat (textured/solid): 0 inches wasted per strip
  • Small repeat (under 6 in): waste 3–6 in per strip
  • Large repeat (18–24 in): waste 12–18 in per strip

Reference: standard wallpaper coverage

The single/double roll thing catches people out, so it is worth being blunt about it. A 33-foot bolt at 20.5 inches wide holds about 56 sq ft of paper, and that bolt is what the trade calls a double roll. “Single roll” is a pricing unit, half a bolt, roughly 28 sq ft, and almost nothing is physically sold that way. So:

• Single roll (a price, not a package): ≈ 28 sq ft
• Double roll (the bolt you actually carry home): ≈ 56 sq ft

Quote the job in single rolls, buy in doubles, and you end up with half the paper you needed. Enter the length of the bolt in your hand and this page does not care what the label calls it.

Worked example: Room wall: 12 ft wide × 9 ft tall. Wallpaper: 20.5 in wide, 33 ft roll, 18-inch pattern repeat.

Strips needed = (12 × 12 inches) ÷ 20.5 = 144 ÷ 20.5 = 7.02 → 8 strips

Strip length = 108 in ceiling height + 4 in trim + 18 in repeat = 130 inches per strip

Strips per roll = 396 in ÷ 130 in = 3.05 → 3 strips per roll

Rolls needed = 8 ÷ 3 = 2.67 → 3 rolls, plus the 10% buffer = buy 4 rolls

That 3.05 is worth staring at. Five hundredths of a strip more and you would still only get three, because a partial drop is offcut. It is also why nudging the repeat down a couple of inches sometimes saves you nothing at all and sometimes saves you a whole roll.

Buy the whole job in one go. Wallpaper is printed in dye lots, and two rolls from different lots can differ enough in colour to show as a visible seam on the wall. Running short halfway through and ordering one more roll is the single most common way a wallpaper job goes wrong. Check the batch number printed on the label of every roll before you start hanging.