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Wallpaper Calculator – How Many Rolls Do I Need?

This wallpaper calculator tells you how many rolls to buy: enter the room length, width and ceiling height, the area of windows and doors, and the size of your roll, and you instantly get the number of rolls. Pattern repeat and drop match are included, because on patterned wallpaper they can add a whole roll or more.

Source: Roman Decorating Products – How to measure for wallpaper and pattern repeats (strips, drop length, straight and drop match). Updated: .

Every second strip is hung half a repeat lower
ft
ft
ft
Floor to ceiling, or up to the chair rail
sq ft
Only strips that drop out completely are deducted
in
Typical US rolls: 20.5 in; some are 27 in
ft
Double roll (bolt) 33 ft, single roll 16.5 ft – check the label
in
0 for plain or random-match papers; printed on the label
My ToolboxYour inputs are saved in this browser only.

Result

Rolls needed
10 rolls
Strips
28 strips of 8.3 ft
Wallpaper used
233.2 ft of wallpaper (370 sq ft of wall)
Rolls by pattern repeat (for your room)
Repeatstraightdrop match
no repeat1010
6 in1010
12 in1010
21 in1010
25 in1010
Working
50 ft of wall ÷ 20.5 in roll width = 30 strips, minus 2 for windows and doors = 28 strips. Strip length: 8 ft height + 4 in trim allowance = 8.3 ft. 3 strips per roll gives 10 rolls.
Buy all rolls at once (same batch or dye lot number) and keep one roll spare – color differences between batches show up later.

How it is calculated

How the wallpaper calculator works

  1. Strips: the width of wall (for a room, the perimeter 2 × (length + width)) divided by the roll width, rounded up. For 50 ft of wall and a 20.5 in roll that is 30 strips.
  2. Strip length: wall height plus 4 in (10 cm) so you can trim top and bottom – 8 ft becomes about 8 ft 4 in. With a pattern repeat, that length is rounded up to a whole number of repeats.
  3. Strips per roll: roll length divided by strip length, rounded down: 33 ft ÷ 8.33 ft = 3 strips.
  4. Rolls: strips ÷ strips per roll, rounded up.

Pattern repeat and drop match

The repeat is the vertical distance after which the pattern starts again. So that the design lines up at the seam, every strip has to start at the same point of the pattern, which means it is cut to a multiple of the repeat and the rest is waste. With a drop match (half-drop) every second strip starts half a repeat lower, which costs half a repeat more for every pair of strips. The table under the result shows how many rolls your room needs at different repeats, so you see the cost of a large pattern before you buy.

Single and double rolls

In the US wallpaper is priced by the single roll but usually packed as a double roll (bolt). A single roll of 20.5 in wallpaper is about 16.5 ft long and covers roughly 28 sq ft, a double roll is 33 ft. Enter the length of one packaged roll as printed on the label – the result is then in packaged rolls; for single rolls, double the number. To convert other measurements, the inches to cm converter and the square footage calculator help.

Windows, doors and slopes

The calculator only removes strips that drop out completely because of an opening; above and below windows pieces still have to be hung, which the trim allowance usually covers. For a sloped ceiling, measure the tallest point of the wall and use that height – slightly generous, but safe. Order one spare roll from the same batch for repairs.

Frequently asked questions

How many rolls of wallpaper do I need for a 13 × 12 ft room?

With 8 ft walls, 30 sq ft of windows and doors and 20.5 in × 33 ft rolls with no repeat, you need 28 strips and 10 rolls. A larger pattern repeat can raise that.

How do I calculate wallpaper with a pattern repeat?

Strip length = wall height + 4 in, rounded up to a multiple of the repeat. With a 25 in repeat and 8 ft walls a strip is 8 ft 4 in = 100 in, exactly four repeats, so a 33 ft roll yields 3 strips.

What is a drop match?

The pattern is printed so that neighbouring strips are offset by half a repeat. The calculator adds half a repeat to every second strip for this.

How much extra wallpaper should I buy?

The 4 in trim allowance per strip is already included. With a pattern the waste is inside the strip length. Buy one extra roll from the same batch as a spare.

How do I calculate wallpaper for one wall?

Choose “One wall only”, enter its width as the length and the height. A 10 ft wide, 8 ft high wall needs 6 strips of 20.5 in, or 2 double rolls.

Sources and legal basis

As of: · Editorial policy

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