Cushion Cover Size Guide: How to Choose the Right Size & Shape
Choosing a cushion cover sounds simple until you start looking at the numbers. 16 inches, 18 inches, 20 inches, lumbar, bolster and suddenly you're wondering what actually belongs on your sofa.
The good news is that there isn't one perfect cushion size. The right size depends on the shape of the cushion, the furniture it sits on and how you want the arrangement to feel.
In this guide, we'll break down the most common cushion shapes and sizes, where each one works best, and how to combine them without making your sofa or bed feel overdone.
First, How Do You Measure a Cushion?
If you already have an insert that you love, measuring it is the easiest place to start.
Measure the width and height from edge to edge, rather than measuring across the diagonal. If the insert has become very flat or compressed with use, measure the cover instead.
Don't measure a squashed-down insert. A well-filled cushion will naturally measure differently when it is lying flat.
And remember: the size of your cushion cover and the size of your insert don't always have to be identical. If you prefer a fuller, plumper cushion, a slightly larger insert can help fill out the corners and give the cover a more generous appearance.
Cushion Covers by Shape
Before worrying about the numbers, it helps to understand the four basic shapes you'll come across.
You don't need to use all four shapes together. In fact, you probably shouldn't.
Think of the square cushion as the foundation, while lumbars, rounds and bolsters are accents that can bring a little variation to the arrangement.
1. Square Cushion Covers
Square cushions are the most versatile of the lot and the ones you'll probably use most often.
16 × 16 inches
A smaller, more decorative scale. It works well in front of larger cushions or on a petite chair where a 20-inch cushion might feel too generous.
18 × 18 inches
In our experience, 18 inches is a sweet spot.
It's substantial enough to look intentional without overwhelming most sofas and chairs. If you're unsure where to begin, 18 inches is a safe place to start.
At Deodar, this is one of our core cushion sizes and the best selling size.
20 × 20 inches
A little more generous and substantial. A 20-inch cushion works particularly well on deeper sofas, larger beds and furniture that can handle a little more visual weight.
The larger the furniture, the more cushion you can usually get away with.
2. Lumbar Cushion Covers
Lumbar cushions are rectangular rather than square, and their proportions make them particularly useful for breaking up a row of square cushions.
Common sizes include 12 × 20, 14 × 20 and 14 × 24 inches.
They work beautifully:
- in front of larger square cushions
- across the centre of a sofa
- on an armchair
- along the front of a bed
- on a bench or window seat
A lumbar doesn't need to be large to make a difference. Its job is often to introduce a different proportion rather than more volume.
3. Round Cushion Covers
Round cushions are less common than squares and lumbars, but they can be lovely accent pieces.
Most are around 16–20 inches in diameter.
Their biggest advantage is visual: a round cushion softens all those straight horizontal and vertical lines around it.
Use one on an armchair, layered on a bed or as a single accent among square cushions.
Because of their shape, rounds usually work best as an accent rather than the foundation of your arrangement.
4. Bolster Cushion Covers
Long and cylindrical, bolsters are another way to introduce a different shape.
They are commonly around 20–24 inches long, although sizes vary.
Bolsters work especially well:
- at the front of a bed
- against the arm of a sofa
- on a daybed
- on a reading chair
They can also be useful where you want a little more support without the visual bulk of another square cushion and they are also in trend these days.
So, Which Cushion Size Goes Where?
This is where scale really matters.
A cushion that looks perfectly proportioned on a deep three-seater can look enormous on a small armchair. Always look at the furniture before you look at the cushion.
These are useful starting points rather than hard rules:
The depth of the furniture matters just as much as its width. A deep sofa can swallow a small cushion, while a petite sofa may not have the depth for several large ones. But in our experience for most Sofa's 18 inches is the sweet spot.
How to Mix Cushion Sizes
A sofa usually looks more considered when the cushions have some variation in scale rather than all being identical.
The easiest approach is to let the larger cushions anchor the arrangement, with a smaller square or lumbar cushion layered in front for example, 20" + 20" + 18" + lumbar. Start with the larger cushions at the back and bring the smaller ones forward.
The right number depends on the width and depth of the furniture, how much of the sofa you want to leave visible, and whether the cushions are meant to be decorative or actually used.
Mixing sizes is one thing, and mixing patterns is another but in our opinion, the two actually go hand in hand. We find ourselves returning to this principle when styling cushions: scale + rhythm + restraint. Let one size or pattern do a little more of the talking, allow another to support it, and don't be afraid to leave some quiet space between them.
If you want to explore this further, we've written more about mixing prints, patterns and textures in our guide to styling cushion covers, and our guide to choosing cushion covers for a modern living room looks at how these ideas work within a larger room.
Remember, there is no prize for having the most cushions on the sofa.
If the furniture is beautiful and the cushions are well chosen, three generous cushions can look far more considered than seven small ones fighting for space.
Don't Forget the Cushion Insert
The insert has more influence on the finished look than you might think.
A cover can be the right size on paper and still look flat if the insert is poorly filled, too flat or too small. For a fuller, more inviting cushion, invest in a good-quality insert with plenty of fill. Down, feather-down blends and good-quality poly fill can all work well, depending on the look and feel you prefer.
The goal isn't just to make the cushion as fat as possible. It should feel full, comfortable and natural holding the same of the cushion cover well.
A little trick: If you want an 18-inch cushion to look especially plump, you can sometimes use a 20-inch insert in an 18-inch cover. This works better with certain fills and constructions, so think of it as a styling trick rather than a rule.
Common Cushion Size Mistakes
Choosing cushions that are too small for the sofa
A large sofa can make small cushions disappear.
Making every cushion exactly the same size
It can work, but introducing one different shape or scale usually makes an arrangement feel more relaxed.
Measuring a flattened insert
An old, compressed insert isn't necessarily an accurate indication of its original size.
Ignoring furniture depth
A 20-inch cushion needs somewhere to sit. Check how much depth you actually have before buying.
Using too many cushions
If you have to move half the sofa's cushions before you can sit down, there may be a few too many.
A Note on Getting It Right
We don't think choosing cushions should feel like a mathematical exercise. There are measurements, of course, and they matter, but once you understand proportion, there is quite a bit of room to play and add personality.
Sometimes an 18-inch cushion is exactly right. Sometimes a deeper sofa asks for something more generous. Sometimes the most successful arrangement is simply the one that leaves enough of the sofa visible to enjoy or it is the juxtaposition and interplay of different sizes, colours and patterns layered together that makes a room feel more you.
Good cushion styling is rarely about getting only the proportions right; it is about how they make you feel at home.
Choosing the right cushion cover is more than simply finding a size that fits your inserts. Fabric, pattern, texture and the way a cushion works with the rest of the room all play a part. If you're still deciding what kind of cushion cover will work best for your home, our guide to choosing cotton cushion covers looks at the materials, finishes and details worth considering.