Rolls of wallpaper typically measure 33′ (10m) long and 21″ (535mm) wide. Therefore, if the room you are decorating has a ceiling height of approximately 9′ (2760mm) you will be able to cut three drops of wallpaper from each roll.
Remember to allow approximately 6″ (150mm) per cut length for trimming the top and bottom of the strip of wallpaper when it’s in place on the wall. You might have to allow more if the wallpaper has a large pattern repeat.
To calculate how many rolls you require measure the walls of the room. If the room is a basic rectangle, you only need to measure two walls because opposite walls are the same length (remember to double-up the numbers in your final calculation).
While you probably could measure the room on your own, it’s much easier, quicker and more reliable if you have somebody help you. One person can hold the tape measure, while the other checks the length and marks down the numbers.
Make a note of all the measurements, rounding up to the nearest inch. Now divide this total by either 21″ or 535mm.
This figure will tell you how many drops of wallpaper you need.
Then, if you get three lengths from each roll divide the number of drops by three to find out how many rolls you require.
The final calculation
- The walls measure 756″ (18900mm) in total and the ceiling height is 9ft (2760mm) allowing three drops from each roll
- 756″ (18900mm) ÷ 21″ (535mm) = 36 drops of wallpaper
- 36 drops of wallpaper ÷ 3 drops per roll = 12 rolls
Based on this calculation I would purchase 13 rolls of wallpaper which includes one spare roll for any mishaps etc.
It’s always better to have too much wallpaper
I always purchase an extra roll just in case any mistakes are made or if the wallpaper becomes damaged in the future. I don’t tend to deduct too much paper for doors and windows from the total as it is always better to have more than you need. Most DIY stores will credit you for any rolls you return and there is nothing worse than the store not having any stock of your chosen paper should you run short.
Planning where to start the wallpapering depends on the room itself, if you have a main feature in the room such as a fireplace then this is your starting point (this applies more to patterned paper, but it is something I have always done regardless of the paper being used).
The first strip of wallpaper you hang should be central to the fireplace and needs to be perfectly vertical (this is where the plumb line is invaluable) as this strip determines how straight the other strips will be.
In an empty room with no feature you can start to paper from any point. I usually start from the edge of an architrave, again making sure the first strip of paper being hung is perfectly vertical.
Beware of batch numbers
When you buy your chosen wallpaper, be sure to check the batch numbers and/or colour number codes on each roll are the same. The reason for doing this is to ensure all rolls have the same pattern and colouring. Two rolls with different batch numbers may vary slightly because they were made at a different time, hence the term ‘batch’.
This doesn’t apply to lining paper, by the way.
Online wallpaper calculators
I appreciate this is a rather old school way of working out how much wallpaper you need to decorate a room, but it works for me!
If you prefer to use an online wallpaper calculator that does all the working out for you, here are some worth checking out. You’ll still need to measure your room before using them.