Wallpaper Calculator: How Many Rolls Do I Need?
Measure around the walls you will cover, enter the roll size and pattern repeat, and get the number of strips, strips per roll and rolls to buy. After switching units, re-enter your measurements.
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Formula
strips = round up (perimeter ÷ roll width), then × (1 + extra%) rounded up
strip length = wall height, rounded up to a whole number of pattern repeats
strips per roll = round down (roll length ÷ strip length)
rolls = round up (strips ÷ strips per roll)
Worked example
Perimeter 40 ft, walls 8 ft, rolls 20.5 in (1.708 ft) wide and 33 ft long, plain paper, 10% extra:
- Strips: 40 ÷ 1.708 = 23.4, so 24; plus 10% = 26.4, so 27 strips.
- Strip length is 8 ft, so one roll gives floor(33 ÷ 8) = 4 strips.
- Rolls: 27 ÷ 4 = 6.75, so 7 rolls.
With a 21 in (1.75 ft) repeat the strip is 5 repeats = 8.75 ft, one roll gives 3 strips and the room needs 9 rolls.
Assumptions
- The perimeter is the full distance around the walls you will paper; doors and windows are not deducted.
- Strips are hung full height with no extra trim allowance beyond the extra percentage and the pattern repeat. Add a few inches to the wall height if you want a trim allowance on each strip.
- The repeat is the vertical distance before the pattern repeats; set it to 0 for plain or random-match paper. Offset (half-drop) patterns can need one more repeat per strip.
- Roll sizes vary by country: check the label for width and length. Metric inputs are in metres and centimetres.
Frequently asked questions
How many rolls of wallpaper do I need for a room?
Divide the distance around the walls by the roll width to get the strips, work out how many strips one roll yields, then divide. For a 40 ft perimeter, 8 ft walls and 20.5 in rolls 33 ft long that is 24 strips, plus 10% = 27, at 4 per roll = 7 rolls.
How does the pattern repeat change the amount?
Each strip is cut to a whole number of repeats so the pattern lines up. With a 21 in repeat an 8 ft wall needs 5 repeats = 8.75 ft per strip, so a 33 ft roll gives 3 strips instead of 4 and the same room needs 9 rolls instead of 7.
Do I need to subtract doors and windows?
Not in this calculator. Strips over doors and windows are still cut full height, and the pieces above and below the openings are usually wasted, so measure the full perimeter. For a very large opening, subtract its width from the perimeter.
How much extra wallpaper should I buy?
Ten percent extra strips covers trimming at the ceiling and floor, mismatches and mistakes. Buy all rolls from the same batch number, because colour can vary between print runs.