Step 1: Measure Your Couch Depth and Back Height
Before you buy anything. Grab a tape measure and get two numbers: the seat depth (from the front edge of the cushion to where the backrest meets the seat) and the back height (from the seat surface straight up to the top of the backrest). Write both down – you’ll reference them constantly.
Most standard couches land in the 20-22 inch depth range. Deep sectionals, the kind you sink into for movie marathons, often run 24 inches or more. That difference changes everything about pillow sizing.
Here’s the rule of thumb: your pillow cover should be roughly. Equal to – or just slightly larger than – the seat depth.
A 20×20 or 22×22 cover sits perfectly on a standard couch, filling the space without overwhelming it. For deeper seating. Step up to 24×24 pillow case covers or even couch pillow covers 26×26 if you want a more relaxed, lounge-worthy look. A pillow case 24×24 is the sweet spot for most sectionals.
Giving you full coverage without the pillow sliding awkwardly into the gap behind your back.
Measure twice, order once – your back will thank you. If you’re still unsure about which sizes work best for your space, check out The Ultimate Guide to Throw Pillow Sizes: 16×16 vs 18×18 vs 24×24 for Your Couch for a detailed breakdown.
Step 2: Match the Cover to Your Existing Insert (or Choose a New Insert Size)
If you already have pillow inserts, skip the guesswork and grab a tape measure. Measure the width and height of the insert (in inches) while it’s fluffed and laid flat.
Then buy covers that are the same size, or 1-2 inches smaller, for a snug, tailored fit. A 16 x 16 pillow cover works perfectly with a 16-inch insert. While an 18-inch insert pairs best with an 18-inch cover.
Common sizes you’ll see on shelves at Target or Wayfair include 16×16. 18×18, 20×20, 24×24, and 26×26, and covers are sold to match these exactly.
Starting fresh? Pick your cover size first, then buy an insert that’s 1-2 inches larger.
For example, a 24 24 pillow case pairs with a 26-inch insert to give that plush, full look without sagging. If your insert measures 21 inches wide. Look for cushion covers 21×21 or size up to 22×22 for a relaxed, casual drape. Either way, you’ll avoid the deflated-pillow look that screams “mismatched.”
Step 3: Consider the ‘Fluff Factor’-How Full You Want the Pillow to Look
Before you buy, decide on the silhouette you’re after. A firm. Plump pillow calls for an insert that’s 2 inches larger than the cover-so a 24×24 pillow cover pairs with a 26×26 insert. That extra inch on each side gives you that crisp, showroom-ready look. Prefer something softer?
Match the insert size to the cover exactly; the pillow will slump a bit, which reads as casual and inviting.
For decorative pillows that rarely get leaned on, go fuller-they hold their shape better and anchor the sofa visually. But if the pillow will actually support your lower back during movie nights. A softer fill (same-size insert) is far more comfortable.
Also, keep in mind that covers shrink a bit after washing; a slightly larger insert helps maintain fullness over time. And for deep sectionals. Don’t be afraid to size up: a 26×26 cover with a 28×28 insert (when available) gives that luxuriously overstuffed look. Even small accent pieces like 12×12 pillow covers benefit from the same rule-just scale the insert accordingly. For a deeper dive into getting that 26×26 look just right, read our How to Choose the Perfect 26×26 Pillow Cover: Sizing, Style, and Fabric Guide.
Common Mistakes: Sausage vs. Baggy
Most pillow cover problems come down to fit. A cover that’s too small for your insert gives you that “sausage” look – tight, lumpy, strained at the seams.
Too large, and you get a baggy, wrinkled pillow that looks messy instead of relaxed. So measure the actual insert before you buy anything. Don’t trust the label. A 20×20 cover doesn’t always fit a 20×20 insert; fill power and loft vary by brand.
If you’re between sizes, go up. A pillow case 24×24 gives a 22-inch insert some breathing room. Though you’ll need to fluff and adjust the fill to hit the corners. For smaller throws.
A 16 x 16 pillow cover pairs well with a 15-inch insert, and cushion covers 21×21 usually fit 20-inch forms. When you’re unsure, pick the larger cover. It’s much easier to fix a loose fit than a tight one.
A Simple Rule of Thumb for Most Couches
If you’re outfitting a standard couch-typically 20 to 22 inches deep-stick with 20×20 to 24×24 pillow covers. That range fits most off-the-shelf inserts snugly without looking deflated or overstuffed. For deep sectionals or chaise lounges (24 inches or more of seat depth).
Bump up to 26×26 or larger; anything smaller will look lost in the expanse. On accent chairs or small loveseats, 12×12 pillow covers are your best bet for a tidy, proportional look.
And if you’re eyeing a bold statement piece, a 40×40 pillow cover works only on oversized floor cushions-not typical couches. When in doubt really. Measure your couch depth and your existing inserts; it takes under five minutes and spares you the return trip. A quick tape check beats guessing every time.
Especially if you’re ordering a 24 24 pillow case online and can’t feel the fabric first. Before you finalize your purchase, also consider the material—our guide on Chenille vs. Canvas vs. Velvet: Which Pillow Cover Fabric Is Right for Your Living Room? can help you pick a fabric that matches both your style and your comfort needs.
