Wallpaper Roll Calculator
Work out how many wallpaper rolls a room needs using the strip method, with pattern repeat and trim allowance.
- Rolls needed
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- Buy with one spare
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- Strips (drops) needed
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- Length of one strip
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- Strips per roll
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- Wall area to cover
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- Paper bought
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- Offcut / waste
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Fine tuning
Windows and small openings are deliberately not deducted — the offcut above and below a window is rarely long enough to reuse. Always buy rolls from the same batch number.
How it works
This calculator uses the standard decorator's strip (drop) method rather than a plain
area division, because wallpaper can only be cut in full-height strips. First it works out the
wall length to paper: either the room perimeter 2 × (length + width) or the figure
you type in, minus the width of any doors you choose to skip. Dividing that by the roll width
and rounding up gives the number of strips: strips = ⌈perimeter ÷ roll width⌉.
Each strip is your wall height plus a trim allowance (10 cm / 4 in by default, for trimming top
and bottom). With a patterned paper the strip is rounded up to a whole number of pattern
repeats — strip = ⌈(height + trim) ÷ repeat⌉ × repeat — so the design lines up
from strip to strip. For an offset (half-drop) match the calculator conservatively adds half a
repeat before rounding, because alternate strips start half a pattern lower. Then
strips per roll = ⌊roll length ÷ strip length⌋ and
rolls = ⌈strips ÷ strips per roll⌉.
Worked example: a 4 m × 3 m room with 2.4 m walls has a 14 m perimeter. With a plain 10.05 m × 53 cm European roll that is ⌈14 ÷ 0.53⌉ = 27 strips of 2.5 m, 4 strips per roll, so 7 rolls — the same answer as a printed wallpaper chart. Everything is calculated in your browser as you type: nothing is uploaded, there is no sign-up and there are no ads.
Frequently asked questions
How many rolls of wallpaper do I need?
Count strips, not square metres. Divide the wall length you are papering by the roll width and round up to get the number of strips. Each strip is your wall height plus about 10 cm (4 in) of trim, rounded up to a whole pattern repeat if the paper has one. Divide the roll length by the strip length and round down for strips per roll, then divide the strips by that and round up. A 4 m x 3 m room with 2.4 m walls and a plain 10.05 m x 53 cm roll needs 7 rolls.
Why does the pattern repeat change the number of rolls?
On a patterned paper every strip has to start at the same point in the design, so each strip is cut to a whole number of repeats. With a 32 cm repeat a 2.5 m drop becomes 2.56 m, which drops a standard roll from four strips to three and pushes a 27-strip room from 7 rolls to 9. An offset or half-drop match wastes a little more again, because alternate strips start half a repeat lower.
Should I deduct doors and windows?
Deduct full-height openings such as doors, which this calculator does when you enter a door count and width. Windows are normally left in: the offcuts above and below a window are rarely long enough to reuse, so deducting them tends to leave you a roll short. Buying one spare roll from the same batch number is standard practice, and the calculator shows that figure too.