How much wallpaper do I need?
Type the room’s length, width and wall height, and the size of your rolls. The wallpaper calculator counts the strips you need and how many each roll gives, then the rolls to buy.
- Rolls to buy
- 9
A 12 ft × 12 ft room with 8 ft walls needs 9 rolls (29 strips, 4 per roll).
- Strips (drops)
- 29
- Length of each strip
- 8 ft
- Strips per roll
- 4
- Wall area
- 384 ft²
Rolls to buy: 9. A 12 ft × 12 ft room with 8 ft walls needs 9 rolls (29 strips, 4 per roll).
How to calculate
Works out how many rolls of wallpaper a room needs from its size, the roll width and length, and the pattern repeat, by counting the strips each roll gives.
Example with the default inputs (Room length 12 ft, Room width 12 ft, Wall height 8 ft, Roll width 20.5 in, Roll length 33 ft, Pattern repeat 0 in, Doors and windows 2, Spare rolls 1): A 12 ft × 12 ft room with 8 ft walls needs 9 rolls (29 strips, 4 per roll).
Method: Strips = ⌈2 × (length + width) ÷ roll width⌉; strip length = wall height rounded up to whole repeats; strips per roll = ⌊roll length ÷ strip length⌋; rolls = max(1, ⌈strips ÷ strips per roll⌉ − ⌊doors and windows ÷ 4⌋) + spare rolls.
- The room is a rectangle and every wall is papered to the same height.
- Each strip starts at the same point of the pattern, so it is the wall height rounded up to whole repeats; leftover paper on a roll shorter than a strip is waste.
- Every 4 ordinary-size doors or windows save one roll (Brewster’s rule); larger openings are not deducted.
- One spare roll by default, as Cole & Son advise, for matching and mistakes. Buy all rolls from the same batch (dye lot).
Worked examples
Each example is checked against the calculator on every build.
- Room length 12 ft, Room width 12 ft, Wall height 8 ft, Roll width 20.5 in, Roll length 33 ft, Pattern repeat 0 in, Doors and windows 2, Spare rolls 1 gives Strips (drops) 29, Strips per roll 4, Rolls to buy 9, Wall area 384 ft².Source: Brewster Wallcovering, Wallpaper Calculator (1 bolt = 56 ft², 20.5 in × 33 ft; deduct 1 bolt for every 4 ordinary doors or windows), https://www.brewsterwallcovering.com/wallpaper-calculator, retrieved 2026-10-02; Cole & Son, Wallpaper Calculator (add an extra roll for pattern matching and waste), https://cole-and-son.com/pages/wallpaper-calculator, retrieved 2026-10-02
- Room length 14 ft, Room width 10 ft, Wall height 9 ft, Roll width 20.5 in, Roll length 33 ft, Pattern repeat 21 in, Doors and windows 4, Spare rolls 1, Price per roll $60.00 gives Strips (drops) 29, Length of each strip 10.5 ft, Strips per roll 3, Rolls to buy 10, Total cost $600.00.Source: Brewster Wallcovering, Wallpaper Calculator (1 bolt = 56 ft², 20.5 in × 33 ft; deduct 1 bolt for every 4 ordinary doors or windows), https://www.brewsterwallcovering.com/wallpaper-calculator, retrieved 2026-10-02; Cole & Son, Wallpaper Calculator (add an extra roll for pattern matching and waste), https://cole-and-son.com/pages/wallpaper-calculator, retrieved 2026-10-02
- Room length 13.12 ft, Room width 9.843 ft, Wall height 8.202 ft, Roll width 20.87 in, Roll length 32.97 ft, Pattern repeat 25.2 in, Doors and windows 0, Spare rolls 0 gives Strips (drops) 27, Length of each strip 8.4 ft, Strips per roll 3, Rolls to buy 9.
- Room length 20.5 ft, Room width 20.5 ft, Wall height 8 ft, Roll width 20.5 in, Roll length 33 ft, Pattern repeat 0 in, Doors and windows 0, Spare rolls 0 gives Strips (drops) 48, Rolls to buy 12.
How it works
The calculator uses the strip (drop) method. Lengths are read back as the exact decimals typed, in the unit typed (exact unit sizes: 1 ft = 0.3048 m, 1 in = 0.0254 m), so a wall that is a whole number of roll widths is not rounded up by float error.
- Perimeter P = 2 × (room length + room width).
- Strips = ⌈P ÷ roll width⌉.
- Length of each strip = the wall height H when the pattern repeat R is 0; otherwise ⌈H ÷ R⌉ × R, so each strip starts at the same point of the pattern.
- Strips per roll = ⌊roll length ÷ strip length⌋. When this is 0 there is no answer: "One strip is longer than a roll: check the wall height, the repeat and the roll length."
- Rolls to buy = max(1, ⌈strips ÷ strips per roll⌉ − ⌊doors and windows ÷ 4⌋) + spare rolls.
The calculator also shows the Wall area P × H (no deduction for openings) and, when a price per roll is typed, the Total cost: rolls × price.
Assumptions:
- The room is a rectangle, and every wall is papered to the same height.
- The paper left on a roll after its last whole strip is waste.
- Brewster’s rule: every 4 ordinary-size doors or windows save one roll. Larger openings, such as a wide patio door, are not deducted.
- One spare roll by default (Cole & Son: add an extra roll for pattern matching and waste).
- Roll sizes differ by maker. The default, 20.5 in × 33 ft, is the US double roll (bolt) in Brewster’s guide.
Limits: room sizes, wall height and roll sizes from 1 cm to 1,000 m; the repeat 0 or from 1 mm to 1,000 m (a repeat above 0 and under 1 mm has no answer: "A pattern repeat is 0 (no repeat) or at least 1 mm."); doors and windows and spare rolls from 0 to 100; price from $0 to $1,000,000.
Worked examples by hand
12 × 12 ft room, 8 ft walls, 20.5 in × 33 ft rolls, no repeat, 2 openings, 1 spare. P = 48 ft = 576 in; 576 ÷ 20.5 = 28.1, so 29 strips. 33 ft ÷ 8 ft = 4.125, so 4 strips per roll. 29 ÷ 4 = 7.25, so 8 rolls; ⌊2 ÷ 4⌋ = 0 saved; + 1 spare = 9 rolls. Wall area 48 × 8 = 384 ft².
14 × 10 ft room, 9 ft walls, 21 in repeat, 4 openings, 1 spare, $60 a roll. P = 48 ft = 576 in, so 29 strips. 108 in ÷ 21 in = 5.14, so 6 repeats: 126 in (10.5 ft) a strip. 396 in ÷ 126 in = 3.14, so 3 per roll. 29 ÷ 3 = 9.67, so 10 rolls; − 1 for 4 openings; + 1 spare = 10 rolls, $600.
4 × 3 m room, 2.5 m walls, 0.53 × 10.05 m rolls, 64 cm repeat, no openings, no spare. P = 14 m; 14 ÷ 0.53 = 26.4, so 27 strips. 2.5 ÷ 0.64 = 3.9, so 4 repeats: 2.56 m. 10.05 ÷ 2.56 = 3.9, so 3 per roll. 27 ÷ 3 = 9 rolls.
20.5 × 20.5 ft room, 8 ft walls, no openings, no spare. P = 82 ft = 984 in = exactly 48 × 20.5 in: 48 strips, 4 per roll, 12 rolls.
Other questions people ask
How do I work out how many rolls of wallpaper I need?
Count strips, not square feet. Divide the distance around the room by the roll width to get the strips, and the roll length by the wall height to get the strips per roll. A 12 × 12 ft room is 48 ft around: 576 in ÷ 20.5 in = 28.1, so 29 strips. A 33 ft roll gives 4 strips of 8 ft, so 29 ÷ 4 = 7.25, which is 8 rolls, plus a spare.
Why not just divide the wall area by the roll area?
Because the paper is cut into strips the height of the wall, and the end of each roll that is too short for a strip is wasted. A 33 ft roll covers about 56 ft², but on 8 ft walls only 32 ft of it hangs. The strip method counts this waste.
How does the pattern repeat change the number of rolls?
Each strip has to start at the same point of the pattern, so its length rounds up to whole repeats. With a 21 in repeat on 9 ft (108 in) walls, each strip takes 6 repeats, 126 in, and a 33 ft roll gives 3 strips instead of 3.67.
Should I subtract doors and windows?
Only a little. Brewster’s rule is to take off one roll for every 4 ordinary-size doors or windows. Small openings still use up most of a strip, so many decorators do not subtract them at all.
How many spare rolls should I buy?
At least one, as Cole & Son advise, for matching the pattern and fixing mistakes. Buy all the rolls at once from the same batch (dye lot), because a later batch can differ in colour.
What size is a roll of wallpaper?
Sizes vary by maker, so check the label. A common US double roll (bolt) is 20.5 in wide and 33 ft long, about 56 ft². Milton & King rolls are 2 ft wide and 32.9 ft long. Many European rolls are about 0.53 m wide and 10 m long.