How to Measure Your Room for Wallpaper (and Know How Much to Order)

You’ve found the wallpaper. You know where it’s going. You’re ready to order. Then you pull out the tape measure. Suddenly, a fairly straightforward decorating decision has become a small geometry problem.

How many rolls do you need? Do you subtract the windows? What about the pattern repeat? And how much extra should you order without spending money on wallpaper that will spend the rest of its life tucked into a closet? 

The good news is that measuring for wallpaper is much easier once you stop thinking about it purely in terms of square footage.

For Hemlock House wallpaper, the most useful calculation is how many 24-inch-wide drops of wallpaper you need to cover your walls, and how long each of those drops needs to be. Once you know those two things, you can determine how much wallpaper to order with considerably more confidence.

How Much Wallpaper Do I Need?

To calculate how much wallpaper you need:

1. Measure the width and height of each wall you plan to wallpaper.
2. Divide the total wall width by 24 inches, the width of each Hemlock House wallpaper roll, to determine how many vertical drops you'll need.
3. Round that number up to the next whole drop.
4. Determine how long each drop needs to be based on your wall height.
5. Allow extra material for trimming and matching the pattern.
6. Choose the appropriate roll length and order enough 24-inch-wide rolls to complete the entire project at once.

The important thing to remember is that wallpaper isn't paint. Two rooms with the same square footage can require different amounts of wallpaper because wallpaper is installed in individual lengths that need to line up with one another. So let's calculate it based on the actual walls.

Before You Measure: Know What You're Ordering

All Hemlock House wallpaper is 24 inches wide and is available in four standard lengths:

• 3 feet
• 6 feet
• 9 feet
• 12 feet

The idea is to let you choose a length relatively close to the height of the area you're wallpapering, rather than buying substantially more wallpaper than the wall requires. If you're wallpapering above 36-inch wainscoting, for example, you don't necessarily need the same amount of wallpaper as someone covering a nine-foot wall from baseboard to ceiling. Longer custom rolls may also be available for interior designers and professional installers working on projects that require them.

Before you start calculating quantity, pull up the product you're planning to order so you can also check its pattern repeat. Hemlock House patterns use a direct match, which means the design lines up horizontally with the adjacent length rather than requiring a more complicated half-drop installation. The repeat still matters, though, because matching the design can affect how much usable wallpaper you get from a length. More on that in a minute.

Step 1: Decide Exactly Which Walls You're Wallpapering

Start by identifying the actual surfaces that will receive wallpaper. Are you covering:

• All four walls?
• The area above wainscoting?
• An alcove?
• Part of a wall around built-ins?

Measure the wallpapered area rather than simply recording the overall dimensions of the room. And if you're doing an entire room, measure every wall individually.

Don't assume two walls that appear identical actually are. This is particularly useful in older homes, which occasionally have their own opinions about right angles. Write each measurement down as you go.

Step 2: Measure the Height of the Wallpapered Area

Next, measure vertically from the bottom of the wallpapered area to the top. For a full-height wall, that's generally from the baseboard area to the ceiling.

If you're wallpapering above wainscoting or another architectural detail, measure only the portion that will actually receive wallpaper.

Take measurements in more than one place, particularly in an older house where floors and ceilings may not be perfectly level. Use the largest measurement when determining the length you need.

And don't plan on a piece of wallpaper ending at precisely the measured height of the wall. You need some additional material so the wallpaper can be positioned and trimmed cleanly during installation.

That means a wall measuring exactly nine feet high should not automatically be treated as requiring exactly nine feet of material without considering trimming and pattern matching.

Step 3: Measure the Width of Every Wall

Now measure horizontally from one end of each wallpapered wall to the other.

Let's say your wall is 118 inches wide. Hemlock House wallpaper is 24 inches wide. Divide 118 ÷ 24 = 4.92. You can't cover a wall with 4.92 vertical drops, so always round up. You need: 5 drops of wallpaper.

That's the basic width calculation: Wall width ÷ 24 inches = number of drops

Then round up to the next whole number. If you're wallpapering multiple walls, repeat the calculation for each wall.

Should I Subtract Windows and Doors?

Usually, don't get too aggressive about subtracting every opening from your measurements.

It seems logical: There's a door there, so I don't need wallpaper behind the door. True. But wallpaper isn't purchased and installed as a bucket of square footage. You're working with continuous vertical lengths.

A drop may run from the ceiling down to the top of a doorway, continue alongside it, or need enough material around a window for positioning and trimming. The pattern also needs to remain aligned with the neighboring drop.

A very large opening may reduce the amount of wallpaper required, but subtracting every window, doorway and outlet from your total square footage can make your calculation artificially tight.

When in doubt, I'd rather calculate conservatively than discover halfway through installation that the theoretical wallpaper covering the window can't somehow be relocated to the six-foot strip beside it.

Step 4: Account for Pattern Repeat

Here's where wallpaper quantity differs most from something like paint. Wallpaper patterns repeat. If one length ends at a particular point in the design, the next length needs to be positioned so the pattern continues correctly across the seam.

All Hemlock House wallpaper uses a direct match, meaning adjacent lengths align at the same horizontal point in the pattern. You don't need to calculate a half-drop match or alternate the placement of every other length. But a direct match can still create some material waste.

Imagine your wall requires a 100-inch drop, but the pattern needs to advance slightly before the next 100-inch section begins in order for the artwork to line up correctly. That additional material matters. The larger the vertical repeat, the more important this can become when calculating how many usable drops you'll get from your wallpaper.

This is also why square footage alone doesn't reliably tell you how much wallpaper to order. The square footage tells us how much wall exists. The width, wall height and pattern repeat tell us how the wallpaper actually needs to cover it.

Step 5: Choose the Appropriate Wallpaper Length

Once you know your wall height, choose the roll length that gives you enough material for the installation. Hemlock House wallpaper comes in: 3' | 6' | 9' | 12' lengths

For example, if you're wallpapering a four-foot-high area above wainscoting, a six-foot length may make considerably more sense than buying wallpaper intended for a full-height wall.

If you're covering a standard-height wall, you'll choose the length that accommodates the wall plus the material needed for trimming and pattern matching.

This is one of the reasons I offer multiple lengths. You can buy wallpaper that more closely corresponds to the amount of wall you're actually covering, rather than automatically purchasing a much longer roll and paying for material you never intended to put on the wall.

How Much Extra Wallpaper Should I Order?

I recommend erring slightly on the side of too much rather than too little. That doesn't mean wildly padding your order. It means not calculating your project so tightly that one measuring error, trimming issue or damaged length leaves you unable to finish the room.

There is another important reason. Hemlock House wallpaper is printed to order. Wallpaper produced in separate print runs can have slight color variation.

If you run out halfway through the project and place another order later, the new wallpaper may not be an exact color match to the wallpaper already on your wall. For that reason, order all of the wallpaper you expect to need for a room at the same time. A little leftover wallpaper is far more useful than one missing drop. Leftovers can also be worth keeping after installation in case a small section ever needs repair.

Example: Measuring an Entire Room

For a full room, use the same method wall by wall. Imagine the room has:

Wall A: 118 inches wide
Wall B: 96 inches wide
Wall C: 118 inches wide
Wall D: 96 inches wide

Calculate each wall:

Wall A: 118 ÷ 24 = 4.92 → 5 drops

Wall B: 96 ÷ 24 = 4 → 4 drops

Wall C: 118 ÷ 24 = 4.92 → 5 drops

Wall D: 96 ÷ 24 = 4 → 4 drops

Total: 18 drops

Now you know the room requires enough wallpaper to create approximately 18 full-height drops, subject to any adjustments for significant openings and the pattern repeat.

From there, use your wall height and the product's repeat to determine which roll length and quantity provide those usable drops. That is much more reliable than multiplying the room's perimeter by its height and ordering wallpaper based solely on square footage.

Four Wallpaper Measuring Mistakes to Avoid

1. Calculating only square footage

Square footage is useful information, but it doesn't account for the way wallpaper is actually installed. Think in drops, not just square feet.

2. Forgetting about pattern repeat

Matching the design can use additional material between drops. Check the repeat for the specific pattern before finalizing your quantity.

3. Buying exactly your measured wall height

Installation requires room for positioning and trimming. A wall height and wallpaper length that are identical on paper may not leave enough working material.

4. Planning to order more later if you need it

Because separate print runs can have slight color variation, this is one place where being conservative pays off. Calculate the entire project and order it together.

Your Wallpaper Measurement Checklist

Before placing your order, make sure you know:

1. The width of every wall you're wallpapering
2. The maximum height of the wallpapered area
3. How many 24-inch-wide drops each wall requires
4. The pattern repeat of your chosen wallpaper
5. The extra length required for trimming and pattern matching
6. Which Hemlock House roll length accommodates your wall
7. The total quantity required to complete the project at once

Once those numbers are accounted for, the quantity stops feeling like guesswork.

Measure Once, Order With Confidence

You don't need to become a wallpaper installer to figure out how much wallpaper your room requires.

Measure each wall. Calculate the number of 24-inch drops. Check your height. Account for the pattern repeat and trimming. Give yourself a sensible margin rather than ordering to the absolute mathematical minimum.

Most importantly, order enough to complete the entire room at once. Finishing with a little wallpaper left over is preferable to getting 90 percent of the way around the room and discovering that your calculation was one drop too optimistic. Once your measurements are ready, choose your Hemlock House wallpaper, select the appropriate length, and order the full quantity you'll need for your project.

Next up: prepare your walls properly before installation, then you're ready to start hanging wallpaper.