Wallpaper Calculator
Works out wallpaper rolls for a room. The pattern repeat is the input that matters — it is why two papers covering the same wall can need different numbers of rolls.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
drop length = ceiling(height × (1 + waste) ÷ repeat) × repeat drops per roll = floor(roll length ÷ drop length) rolls = ceiling(drops ÷ drops per roll)
Both roundings go against you, which is why area-based estimates run short. A drop has to start at the same point in the pattern every time, so it is rounded up to a whole number of repeats; and only whole drops come off a roll, so the remainder is scrap.
What to watch out for
Wallpaper is not bought by area, and treating it that way is how people run short:
- Drops, not square metres. The wall is divided into vertical strips one roll-width across. A part-width strip still uses a full drop.
- The repeat is wasted on every drop. A 64 cm repeat on a 2.4 m wall means each drop is cut at 2.56 m, so 16 cm goes in the bin every time.
- Only whole drops come off a roll. A 10.05 m roll giving three 2.6 m drops leaves 2.2 m unusable.
- Check batch numbers. Different batches of the same paper differ in shade, and on a feature wall it is obvious.
Buy one spare roll. Matching a batch later is usually impossible, and damage happens.
Frequently Asked Questions
How many rolls of wallpaper do I need?
Divide the room perimeter by the roll width for the number of drops, work out how many drops come off a roll, then divide. A 4 × 3.5 m room with 2.4 m walls and a plain paper works out at 27 drops, three to a roll — so 9 rolls.
How does the pattern repeat affect how much I need?
Every drop is cut to a whole number of repeats, so a large repeat wastes a slice off each one. A 64 cm repeat on a 2.4 m wall adds 16 cm of waste per drop, which can easily add a roll to the order.
How many drops are in a roll of wallpaper?
It depends on the drop length, which is the wall height plus trim plus any pattern repeat. A standard 10.05 m roll gives four drops up to 2.5 m each, three up to 3.35 m, and two beyond that.