How to Calculate How Much Wallpaper You Need

Wondering how much wallpaper you need? It is always best to allow for a little extra, partly in case a strip tears by accident but also in case you can’t get any more wallpaper in the same batch which would mean one strip or one roll would look different.

All it takes is a little time and patience, a metal measuring tape, a pad and pencil and a calculator.

Here’s how to work it out:

1. Let’s take a single blank wall first with a wallpaper that has a plain design.

Measure the width of the wall and the height from top of the skirting to the ceiling.

e.g. 178 inches wide and 104 inches high.

Most wallpapers are 20.5 inches in width (so double check the width). Divide 178 by 20.5 (the width of the wall by the width of the wallpaper to work out how many strips you need) = 8.6 = 9 strips of wallpaper.

The rolls tend to be 11 yards long, so divide 396 by 104 (the height of the wall) = 3.8. Now, if you don’t want to havehorizontal joins along your wall, so this means you will only get 3 full strips per roll.

As you need 9 strips @ 3 full strips per roll, you need 3 rolls of wallpaper.

2. Let’s calculate wallpaper for a single blank wall with a wallpaper that has a repeat design.

Imagine the wall is 155 inches wide, 102 inches in height.

The wallpaper is 20.5 inches wide, 396 inches in a roll (which is standard) and the repeat is 19 inches.

Divide 155 by 20.5 to work out the number of strips needed = 7.56 = 8 strips of wallpaper.

Divide the height by the repeat, 102 divided by 19 = 5.36 which means that 6 repeats is needed in each strip of wallpaper so you now need to multiply 19 x 6 = 114 inches.

(Each strip of wallpaper must be 114 inches cm and there will be 12 inches of waste on each strip.)

Divide the length of the roll by the ‘new’ height, 396 divided by 114 = 3.47 which means that there are 3 full strips in each roll. (half strips can be used above doors and above and below windows but not in an unbroken wall).

Hence as you need 7 strips of wallpaper and there are 3 full strips in each roll, you need 3 rolls of wallpaper.

3. To calculate wallpaper for a full room with doors and windows:

Measure the height and width of the full room (adding together the widths of all four walls). While you may think that you can subtract the width of the doors and the windows, you can’t! The reason is the part of a full strip (lengthways) may be used beside the door and the waste from that cannot be used. Hence, I would advise only subtracting half the width of the doors and windows (and remember you will need wallpaper above and below the window).

Full width of room = 483 inches

Height = 104 inches

Repeat of wallpaper = 22 inches.

Divide the height by the repeat, 104 divided by 22 = 4.72 so 5 repeats are needed. 22 x 5 = 110 inches per strip.

Divide the full width of the room by the width of the wallpaper, 483 divided by 20.5 = 24 strips.

If there are 2 doors in the room, I would subtract one strip.

I would only subtract one strip of wallpaper for every 2 or 3 windows in the room – better to err on the side of caution. It is possible to work out exactly how much wallpaper is require but you would need to know your starting point in the room and the exact measurements above and below the window

Divide 396 by 110 to work out how many strips you will get out of each roll = 3.6 which is 3 full strips. Part of the remainder could be used above doors and above windows. Hence, for a room with 2 doors and 3 average sized windows, I would order order 22 strips for this room (24 minus 2) which is 8 rolls.

If in doubt, double check using a wallpaper calculator which is often available on sites that sell wallpaper or check with your decorator.

I hope that helps you to calculate how many rolls of wallpaper you will need for your decorating.

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