How to use the wallpaper calculator
- Enter the room’s length, width and wall height. Measure the height in several places; older ceilings are often uneven, and the tallest point sets the strip length.
- Count the doors. Each door removes one door width from the wall run; windows are not deducted because paper is still hung above and below them.
- Copy the roll width, roll length and pattern repeat from the roll label. Use 0 for plain paper or a random match.
- Keep the waste allowance at 10% unless the paper is very expensive and the room is simple.
- Read the rolls to buy, then use Copy result or Print list before you order.
How the roll count is worked out
Area-based estimates (“square feet ÷ roll coverage”) often come up short, because each strip has to be cut to a whole number of pattern repeats and the leftover end of a roll is usually too short to use. This calculator follows the paperhanger’s method instead.
Strips = wall width ÷ roll width, rounded up
Strip length = wall height + trim, rounded up to a whole number of repeats
Strips per roll = roll length ÷ strip length, rounded down
Rolls = strips × (1 + waste %) ÷ strips per roll, rounded up
Worked example
A 12 × 10 ft room with 8 ft walls and one 3 ft door, using US double rolls 20.5 in wide and 33 ft long, a 21 in pattern repeat, 4 in for trimming and 10% extra strips:
- Wall width: 2 × (12 + 10) − 3 = 41 ft, which needs 24 strips of 20.5 in.
- Each strip: 96 + 4 = 100 in, rounded up to five repeats of 21 in = 105 in.
- One 33 ft roll is 396 in long, so it gives 3 full strips.
- With 10% extra the job needs 27 strips, so buy 9 rolls, which at $45 a roll comes to $405.00.
Tips and common mistakes
- Check the batch number. Rolls printed in different runs can differ slightly in colour. Buy every roll with the same batch or lot number, and one spare for repairs.
- Know your match type. A straight match lines up across the same height on every strip. A drop (offset) match shifts by half a repeat, which can cost one extra strip per wall; raise the waste allowance a little for it.
- Prepare the walls first. Fill cracks, sand, and seal new plaster or drywall with a primer made for wallpaper so it can be removed later without tearing the surface.
- Plan the first strip. Start from a corner or the middle of a feature wall with a plumb line, never by trusting a corner to be straight.
US, UK and Canada differences
In the United States, wallpaper is usually priced per single roll but sold packaged as double rolls; a common double roll is about 20.5 in wide and 33 ft long. Enter the size of the roll you will actually receive. In the UK and Europe, the standard roll is 0.53 m wide and 10.05 m long, sold and priced singly, and lining paper is often hung first on old plaster. Canadian stores stock both North American and European sizes, so read the label rather than assuming.
Metric units and other countries
In metric mode, enter room sizes in metres, roll width and pattern repeat in centimetres and roll length in metres. Imported European rolls are widely sold in South Asia and the Gulf as well, and wider 0.7 m or 1 m rolls also exist, so take the numbers from the label of the paper you choose and type your local price per roll.