Finding the right size pillow cover for an 18×18 insert can be tricky. You want a snug, polished look without any bunching or pulling. This guide will explain exactly what you need to know to get that perfect fit every single time.
It’s a common mistake to think an 18×18 pillow needs an 18×18 cover. That actually leads to a overstuffed, tight appearance. The secret lies in understanding a simple rule of thumb used by designers and home decor enthusiasts. Let’s break it down so you can confidently shop or sew your next pillow cover.
What Size Pillow Cover For 18×18 Insert
The ideal pillow cover size for a standard 18×18 inch insert is 17×17 inches. This one-inch difference is the golden rule for achieving a plump, professional finish. A cover that is slightly smaller than the insert ensures the pillow looks full and avoids a saggy or deflated appearance.
This rule applies to most pillow types, from decorative throw pillows to bed shams. The tight fit keeps the insert from shifting and creates crisp corners. Remember, pillow inserts are measured by their dimensions when full and plump, not compressed.
Why the Cover Should Be Smaller Than the Insert
Using a smaller cover serves two main purposes. First, it eliminates excess fabric that can wrinkle or look messy. Second, it puts gentle pressure on the insert, making it appear more luxurious and firm. Think of it like putting a fresh case on a fluffy down comforter—it always looks best when it’s snug.
If you use an 18×18 cover on an 18×18 insert, the fit will be too exact. The pillow will look flat and the corners might not fill out properly. It can also cause the insert to shift around inside the cover, leading to uneven lumps.
Exceptions to the One-Inch Rule
While 17×17 is the standard recommendation, there are a few situations where you might adjust the size.
- Very Thin or Flat Inserts: If your 18×18 insert is underfilled or made of a flat material like foam, a 17.5×17.5 inch cover might be better.
- Extremely Thick or Feather Inserts: For a super plush down insert, you might even go down to a 16.5×16.5 cover for an extra-full look.
- Certain Fabric Types: Stiff, non-stretch fabrics like heavy linen or canvas might require a cover that’s only half an inch smaller (17.5×17.5) for easier insertion.
Measuring Your Existing Insert
Before you buy or make a cover, it’s smart to double-check your insert’s true size. Inserts can vary slightly from their labeled dimensions.
- Lay the insert flat on a hard surface.
- Use a soft measuring tape to measure from seam to seam across the center.
- Measure both the width and the height.
- Note if the insert seems underfilled or overly firm.
This quick step ensures you’re starting with the right information. An insert that’s actually 18.5 inches full will need a different cover than one that’s a true 18.
Choosing the Right Closure Style
The closure on your pillow cover affects both the look and the final fit. Different closures can accommodate the tight fit of a smaller cover more or less easily.
Envelope Closure
This is a popular and simple style with a overlapping flap in the back. It’s great for a clean look and relatively easy to insert the pillow. Because the opening is not as constricted, it works very well with the 17×17 cover for an 18×18 insert rule.
Zipper Closure
A zipper closure, usually along one side or the bottom, gives a very finished appearance. It allows for the tightest fit because you can fully open the cover. When using a zipper, ensure the fabric doesn’t get caught. A 17×17 cover with a zipper is an excellent choice for a tailored look.
Knife-Edge or Slipcover Style
These covers are open on one end with no formal closure. You simply tuck the insert inside. They often work best when the cover is exactly the insert size or even slightly larger, as tucking a too-small cover can be difficult. For an 18×18 insert, an 18×18 knife-edge cover is usually preferable.
Step-by-Step Guide to Sewing Your Own 17×17 Cover
Making your own pillow cover is a rewarding project. Here’s how to sew a simple envelope closure cover for your 18×18 insert.
Materials You Will Need
- Fabric of your choice (about 1/2 yard for one cover)
- Thread
- Scissors or rotary cutter
- Sewing machine
- Measuring tape
- Straight pins
Cutting the Fabric Pieces
- Cut one front panel: 17.5 inches by 17.5 inches. (The extra half-inch is for seam allowances).
- Cut two back panels: For the envelope flap, cut two pieces that are 17.5 inches wide by 12 inches tall each.
These dimensions include a standard 1/4-inch seam allowance on all sides. If you prefer a larger seam allowance, adjust your cutting size accordingly.
Sewing the Cover Together
- Hem one long edge (the 17.5 inch side) on each of the two back panels. Fold over 1/4 inch, press, then fold over another 1/2 inch, press, and stitch down.
- Lay the front panel right side up. Place the two back panels on top, right sides down, with their hemmed edges overlapping in the center. The raw edges of all pieces should align.
- Pin all the way around the square.
- Sew around all four edges using a 1/4-inch seam allowance.
- Clip the corners diagonally to reduce bulk, being careful not to cut the stitching.
- Turn the cover right side out, push out the corners gently, and press it flat with an iron.
Now your custom 17×17 cover is ready for your 18×18 insert. The fit should be perfect and plump.
Buying Pre-Made Covers: What to Look For
When shopping for a ready-made cover, product descriptions can be confusing. Here’s how to navigate them.
Reading Product Descriptions Carefully
Many retailers list the cover size, not the recommended insert size. A listing for a “17×17 Pillow Cover” is telling you the finished cover dimensions. This is perfect for your 18×18 insert. However, some might list it as “Fits 18×18 Insert” while selling a 17×17 cover. Always check the detailed dimensions if provided.
Common Retailer Sizing Charts
Most reputable home goods stores provide a sizing guide. They will often explicitly state: “For an 18×18 insert, order a 17×17 cover.” If this chart exists, always follow it over the product title alone. Don’t assume the sizes match directly.
Considering Stretch Fabrics
Covers made from stretchy materials like jersey knit or certain velvets can sometimes accommodate a wider range. A stretchy 18×18 cover might still give a good fit on an 18×18 insert because the fabric gives. But for structured look, sticking to the smaller size is still the best bet.
Fixing Common Pillow Cover Problems
Even with the right size, you might encounter a few issues. Here’s how to solve them.
Cover is Too Tight and Won’t Close
If you can’t get the insert into the cover or can’t close the zipper, the cover is too small. This can happen if your insert is thicker than average. Try a cover that’s half an inch larger. You can also try a different closure style, like an envelope, which might be more forgiving than a zipper in this case.
Cover is Too Loose and Looks Saggy
A loose, wrinkly cover means it’s too big. The insert isn’t filling it out. The solution is to use a smaller cover. If you’ve already bought it, you can sometimes take in the seams if you have basic sewing skills. Alternatively, you can use a larger, fuller insert to fill the space, like upgrading to a 19×19 insert for an 18×18 cover.
Corners Aren’t Filling Out
This is a classic sign of using a cover that’s the same size or too big for the insert. The insert’s corners don’t have enough pressure to push them into the cover’s corners. Switching to a cover that is 1-2 inches smaller than the insert will almost always solve this problem immediately.
FAQs: Your Pillow Cover Questions Answered
What size pillow cover for an 18×18 pillow form?
You should use a 17×17 inch pillow cover for an 18×18 pillow form or insert. This ensures a full, plump appearance without wrinkles.
Can I use an 18×18 cover for an 18×18 insert?
You can, but it will likely look flat and the corners may not fill properly. For a premium, tailored look, a slightly smaller cover is always recommended by designers.
How much smaller should a pillow cover be than the insert?
The general rule is 1 to 2 inches smaller in both dimensions. For an 18×18 insert, a 17×17 or even 16×16 cover (for a very full look) is ideal.
What if my 18×18 insert is feather and down?
Feather and down inserts are extra fluffy. You might prefer a cover that is 1.5 to 2 inches smaller (like 16.5×16.5 or 16×16) to really showcase the plushness and prevent shifting.
Do I need to pre-wash fabric before making a cover?
Yes, it’s a good idea to pre-wash and dry your fabric the same way you plan to launder the finished cover. This prevents any unexpected shrinkage after you’ve sewn it, which could make the cover to tight later on.
Special Considerations for Different Materials
The fabric of your cover plays a big role in the final fit and feel.
Linen and Cotton
These natural fibers have little to no stretch. They provide a crisp, structured look. Because they don’t give, adhering strictly to the 17×17 cover for an 18×18 insert rule is important. You might even find a 16.5×16.5 cover gives a wonderful, full shape with these materials.
Velvet and Minky
These fabrics are thicker and sometimes have a slight stretch or nap. They can be more forgiving. A 17×17 cover will work beautifully, but a 17.5×17.5 might also fit well and be easier to get the insert into due to the fabric’s thickness.
Outdoor and Performance Fabrics
Fabrics like Sunbrella are very sturdy and have no stretch. They often require precise sizing. Follow the one-inch rule exactly, and consider an envelope closure for easiest use, as zippers can be tricky with thick, weather-resistant fabric.
Conclusion: Achieving the Perfect Look
Getting the right size pillow cover for an 18×18 insert is simple once you know the secret. Remember, the cover should be smaller than the insert—aim for 17×17 inches as your starting point. This creates the full, professional finish you see in well-decorated homes.
Whether you’re shopping online, reading a label in store, or cutting fabric for a DIY project, keep this rule in mind. Always consider the insert’s fullness and the cover’s closure style as they can fine-tune the fit. With this knowledge, you can say goodbye to saggy, wrinkled pillows and hello to perfectly plump, inviting accents on your sofa or bed. Your decor will look more intentional and polished instantly.