How Much Do I Need?

Wallpaper Calculator

How much wallpaper do I need?

Enter the walls you are papering, the roll size and the pattern repeat from the label. The calculator works out how many full-height strips (drops) you need and how many you can cut from each roll, then rounds up to whole rolls.

Units
Walls

From the top of the skirting board or floor to the ceiling.

Add up the widths of doors and large windows. Leave small windows in: the paper above and below still has to be cut from full drops.

Wallpaper roll

Common sizes: 20.5 in (US) or 53 cm (European standard).

A US double roll is usually about 33 ft; a European roll is 10.05 m. Check the label.

On the label. Enter 0 for plain or random-match paper.

Extra at top and bottom for trimming. 4 in (10 cm) is typical.

Spare paper for a mistake or a later repair, from the same batch.

Cost (optional)

Add the price to see an estimated total.

Results update as you type.

Your estimate

Wallpaper to buy

9 rolls

24 drops of 100 in, 3 from each roll, plus 10% extra.

Estimated amount to buy

Rolls
9 rolls
Rolls with no extra
8

Calculated quantity (no extra)

Width to paper
41 ft
Wall area
328 ft²
Drops (full-height strips)
24
Drops you can cut per roll
3
Rolls by area alone (for comparison)
5.82
How this was calculated
  1. Wall width = 2 × (12 ft + 10 ft) − 3 ft of openings = 41 ft
  2. Drops = 41 ft ÷ 20.5 in roll width = 24, rounded up to 24
  3. Drop length = 8 ft + 4 in trim = 100 in
  4. Drops per roll = 33 ft ÷ 100 in = 3.96, rounded down to 3
  5. Rolls = 24 drops ÷ 3 per roll = 8, rounded up to 8
  6. With 10% extra = 8 × 1.1 = 8.8, rounded up to 9
  • The drop count is more reliable than dividing the wall area by the roll area, because the offcut at the end of each roll is usually too short to use.
  • Buy every roll from the same batch (lot) number: colours can differ slightly between batches.

How the wallpaper calculation works

Decorators count wallpaper in drops: full-height strips cut from the roll.

  1. Width to paper = the walls' total width (2 × (length + width) for a whole room) minus doors and large windows.
  2. Drops = width to paper ÷ roll width, rounded up.
  3. Drop length = wall height + trim allowance. With a patterned paper this is rounded up to a whole number of pattern repeats, so each strip lines up with the next.
  4. Drops per roll = roll length ÷ drop length, rounded down, because a short leftover piece can't make a full drop.
  5. Rolls = drops ÷ drops per roll, rounded up, then the extra is added and rounded up again.

Why pattern repeat matters

A large pattern repeat can use a lot more paper. For example, with 8 ft (2.44 m) walls and a 21 in (53 cm) repeat, each drop must be long enough for five repeats, 105 in (2.67 m), even though the wall only needs about 100 in with trim. A 33 ft (396 in) roll then gives three drops, leaving an 81 in offcut that is too short for a fourth.

Rounding rules

  • Drops are rounded up; drops per roll are rounded down.
  • Rolls are rounded up, before and after the extra is added.
  • Measurements are converted exactly, so you can enter the room in feet and the roll width in centimetres.