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About this tool
Work out how many wallpaper rolls a room needs using drop lengths, pattern repeat and roll size, with waste and cost included.
The Wallpaper Calculator tells you how many rolls to buy for a room by working in drops, the way decorators actually do it: drops needed = wall run / roll width, drops per roll = roll length / drop length rounded down, rolls = drops needed / drops per roll rounded up. It handles the three trade pattern-match types — free, straight and half-drop offset — because a pattern repeat forces each drop to be cut to a whole number of repeats and can add several rolls to the same room. Use it before you order, when a discontinued batch means a second order is not an option.
Open Wallpaper Calculator on AltFTool — it loads instantly in your browser.
Enter the values you already know.
Fine-tune the options to match your scenario.
Read the result and use it in your planning or reporting.
Drops per roll are rounded down and rolls are rounded up, so you never end up one drop short.
Straight match rounds each drop up to a whole repeat; half-drop match adds the customary extra half repeat first.
Reports offcut left on each roll, spare drops and total waste percentage, so you can see what the pattern is costing you.
With 2.4 m ceilings, a free-match paper and a standard 10.05 m x 53 cm roll: the perimeter is 14 m, so 14 / 0.53 = 27 drops; each drop is 2.5 m including trim, so 10.05 / 2.5 = 4 drops per roll; 27 / 4 rounds up to 7 rolls.
The European standard roll is 10.05 m long and 53 cm wide, which is 5.33 square metres of paper. Wide Euro rolls are 70 cm, and an American single roll is 27 inches wide by about 4.6 m long.
Yes, often by two or three rolls. On a straight match every drop is cut to a whole number of repeats, so a 2.5 m drop with a 64 cm repeat becomes 2.56 m — that drops the yield from 4 drops per roll to 3, taking a 14 m room from 7 rolls to 9.
Only full-height openings such as patio doors are worth deducting from the wall run; decorators paper past standard windows and doors and trim, because the offcut rarely fits anywhere else. Add one spare roll if the paper is a limited batch.
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