Donaldson R F Wallpaper Calculator
Find out how many rolls you need for a room — allowing for doors, windows, cutting allowance and pattern repeat.
Wallpaper roll
How the calculation works
Wallpaper is hung in vertical strips, so the calculator counts strips rather than just square metres. The number of strips is the total wall length divided by the roll width (rounded up). Each strip is as long as the wall height plus 10 cm to trim at the ceiling and skirting board; with a pattern repeat, the length is rounded up to the next full repeat so the pattern lines up from strip to strip. The number of strips that fit in one roll is the roll length divided by the strip length (rounded down), and the rolls needed is strips ÷ strips per roll, rounded up. A door saves the strips that fit fully within its width; windows and other partial openings are not deducted, because you still need paper above and below them. Always buy all rolls from the same batch, and consider one spare roll for repairs or if you are unsure of your measurements.