Wallpaper has a reputation for being difficult to apply. Even before you start wrestling with paste and paper, you must determine how much wallpaper you need.

Fortunately, I’ve created this handy wallpaper calculator so you can easily determine the number of rolls you need for your next decorating project.

Wallpaper Calculator

Follow the steps below to calculate how many wallpaper rolls you need for one wall.

1. Measure Wall Width and Height

Using a tape measure, measure the width and height of the wall you want to cover.

Unless you have a window that is essentially a glass wall, don’t subtract space for doors and windows. This extra space will ensure you have enough spare wallpaper.

2. Find the Wallpaper Width

This measurement will be in the manufacturer’s sample book or wallpaper packaging.

3. Divide Wall Width by Wallpaper Width

This calculation gives you the number of rolls it will take to cover the width of your wall.

You might think, great, I’m done. Not so fast!

Each one of these rolls is typically 10m long. That means you can ‘drop’ multiple floor-to-ceiling lengths of wallpaper from one roll, each drop providing the same width. Therefore, we only need a fraction of the number of rolls calculated in this step.

The next two steps determine this fraction…

4. Find the Wallpaper Length

Again, this measurement will be in the manufacturer’s sample book or wallpaper packaging.

5. Divide Wall Height by Wallpaper Length

Unless the height of your wall is longer than a roll of wallpaper (very unlikely), this number will be a fraction. For example, if a wall is 2.4m meters high and the roll length is 10m, this number will be 0.24. This means we only need 24% of one roll to complete one ‘drop’. In other words, each roll provides 4.17 drops.

Note that this number is affected by the pattern repeat margin, which the manufacturer should provide. I.e wallpaper lengths must pattern match at the edges. The margin is only a few inches for small prints, like polka dots. However, for bold prints (e.g. life-size tropical birds that are currently in vogue), the pattern repeat margin will be much higher, meaning you will need more rolls.

For wallpaper with a complicated pattern, it’s best to ask a sales assistant for help with calculations. When in doubt, always go by the manufacturer’s guidelines.

6. Multiply Step 3 by Step 5

If you have a decimalised number, always round up, so 2.1 becomes 3 rolls, 4.6 becomes 5 rolls and so on.

7. Add on an Extra Roll

Always add on an extra roll. There is nothing worse than wallpapering most of a room, only to run out of paper and find out that the shop you bought it from has sold out.

Most stores will allow you to return unused rolls but check when you purchase.

Example Calculation for One Wall

Note that all numbers below are in meters. Always use a common unit of measure when running the calculations.

Wall width = 4.5m
Wall height = 2.4m
Roll width = 0.52m
Roll length = 10m

4.5m (wall width) divided by 0.52m (roll width) = 8.654
2.4m (wall height) divided by 10m (roll length) = 0.24
8.654 x 0.24 = 2.08.
Round up = 3.
Add an extra roll = 4 rolls to buy.

Remember that the calculation above is for one wall only, so repeat it for any other walls that need covering.

Pro Tip: House Beautiful recommends checking the batch number on each wallpaper roll is the same. There are slight differences in dye lots in different batches, which will be noticeable when the paper is up.

Final Thoughts

So that’s how to calculate how much wallpaper you need. Remember, when in doubt, check with the manufacturer or store.

BTW, if you’re planning on decorating a feature wall, make sure you read our guide on wallpapering a feature wall.