Finding the right insert for your pillow cover can be tricky. If you’re wondering what size insert for 18×18 pillow cover you need, the simple answer is usually an 20×20 inch insert. This one-size-up rule creates a plump, professional look that avoids a saggy or flat appearance. Getting this fit right makes all the difference in your home decor.
This guide will explain exactly why sizing up is key. We’ll cover how to measure, the best materials, and tips for different pillow styles. You’ll learn how to achieve that perfect, full look every time.
What Size Insert For 18×18 Pillow Cover
The golden rule for pillow inserts is to choose one that is 2 to 4 inches larger than your cover. For an 18×18 inch cover, this means you should select a 20×20 inch insert. This size difference is not a mistake—it’s intentional. The larger insert fills the cover completely, ensuring no empty corners or a deflated look.
Using an insert that matches the cover’s exact dimensions often results in a pillow that looks under-stuffed and sloppy. The fabric won’t be taut, and the pillow will lack shape. A 20×20 insert provides the resistance needed to make the cover look crisp and inviting.
Why a Bigger Insert is Better
Think of your pillow cover like a shirt. If you wear your exact size, it fits. But if you want a very tailored, filled-out fit, you might size down. For pillows, we size up the insert instead. The extra volume pushes against the seams, creating a luxuriously plump profile.
- Avoids Wrinkles: A larger insert smooths out the cover fabric.
- Provides Structure: It gives the pillow a defined, square shape.
- Improves Durability: A full cover experiences less friction and wear from the insert moving around inside.
What If You Prefer a Softer Look?
Some decor styles, like a casual, relaxed farmhouse look, benefit from a softer pillow. In this case, you can use an 18×18 insert. It will give a more loungy, less formal appearance. Just know that it may shift more inside the cover and require frequent fluffing.
For down or feather blends, you can even consider a 22×22 insert if you want an extremely full, overstuffed chair pillow. The compressible nature of feathers allows it to fit into the smaller cover while maintaing incredible fullness.
Measuring Your Cover Correctly
Always measure your pillow cover before buying an insert. Use a soft measuring tape and measure from seam to seam. Measure both the width and the height. If the cover is already made, flatten it gently without stretching. Confirm it is truly 18×18 inches, as sometimes there can be slight variations.
Choosing the Right Insert Material
The material inside your pillow is just as important as the size. It affects the feel, shape, and price. Here are the most common options.
Polyester Fiberfill (Standard)
This is the most common and affordable type. It’s hypoallergenic, firm, and holds its shape well. It’s a great choice for everyday use on sofas and beds. Look for terms like “high loft” for a plumper feel. A 20×20 fiberfill insert will give your 18×18 cover a consistent, sturdy shape.
Down and Feather Blends
These inserts offer a luxurious, sink-in softness that molds to your body. They are more expensive but provide a high-end look. A blend (like 95% feathers, 5% down) offers more structure than 100% down. For an 18×18 cover, a 20×20 or even 21×21 down blend insert creates a beautifully decadent pillow.
- Pros: Molds to shape, very soft, long-lasting.
- Cons: Can require frequent fluffing, not suitable for those with allergies, higher cost.
Memory Foam
Memory foam inserts provide exceptional support. They are ideal for lower back pillows on a bed or for chair seating where you want to maintain a specific posture. They are less common for decorative throw pillows but perfect for functional use. A 20×20 memory foam insert will be very firm in an 18×18 cover.
Kapok or Natural Fibers
These are eco-friendly alternatives, often derived from silk floss or plant fibers. They are soft, lightweight, and biodegradable. They can compress over time more than polyester but are a wonderful natural choice. Sizing up 2 inches is still recomended here.
Step-by-Step: Inserting into Your Cover
Getting a large insert into a smaller cover takes a simple technique. Follow these steps to make it easy and avoid damaging the seams.
- Turn the Cover Inside Out: Start by turning your pillow cover completely inside out. This might seem backwards, but it helps.
- Place the Insert: Set your 20×20 insert squarely in the center of the inside-out cover. Align the corners of the insert with the seams of the cover as best you can.
- Roll or Fold the Insert: Gently roll the insert from the opposite side of the cover’s opening. If it has a zipper, roll towards the zipper. This compresses the insert.
- Begin to Pull the Cover Over: Start pulling the cover right-side-out over the rolled insert. Work slowly, easing the fabric over the bulk.
- Adjust and Fluff: Once the cover is fully on, reach into each corner and pull the insert firmly into place. Give the whole pillow a good shake and punch to distribute the filling evenly.
Common Problems and Solutions
My Pillow Still Looks Lumpy or Flat
If you’ve used a 20×20 insert and your pillow isn’t looking full, the insert might be under-stuffed. Check the fill power or weight. A heavier insert (e.g., 24 oz for a 20×20) will be plumper than a light one. You may need to add a bit of loose fiberfill through the cover opening to boost volume.
Corners Won’t Fill Out
This is a classic sign of an insert that’s too small or has shifted. Before closing the cover, always manually push the insert’s corners into the cover’s corners. For stubborn cases, use a chopstick or the end of a spoon to gently push the filling into the very tip of the corner.
Zipper Strain or Bulging
If the zipper area is bulging or looks strained, the insert is likely too big. While a 20×20 is standard, some brands’ 20×20 inserts can run large. Try a different brand or a 19×19 insert. Alternatively, you can remove a small amount of filling from the insert to reduce the volume slightly.
Care and Maintenance Tips
To keep your pillows looking their best, proper care is essential. It extends the life of both the cover and insert.
- Use Pillow Protectors: Place a thin pillow protector over the insert before putting on the decorative cover. This shields it from dust and oils and makes cleaning easier.
- Fluff Regularly: Give your pillows a good shake and punch every few days. This prevents the filling from clumping, especially important for down and fiberfill.
- Spot Clean Covers: For fabric covers, spot clean spills immediately to prevent stains. Check the care label for washing instructions.
- Wash Inserts Sparingly: Polyester inserts can usually be machine washed on gentle and tumble dried on low with tennis balls to re-fluff. Down inserts require special down soap and very thorough drying to prevent mildew.
FAQs: Your Questions Answered
Can I use an 18×18 insert in an 18×18 cover?
You can, but it will likely look flat and the fabric may wrinkle. For a full, professional look, sizing up is strongly recommended. An 18×18 insert is best only if you deliberately want a very soft, casual appearance.
What is the best insert for an 18 inch pillow cover?
The best insert is typically a 20×20 inch polyester fiberfill or down alternative insert. It provides the perfect balance of fullness, affordability, and ease of care for most homes.
How much bigger should a pillow insert be?
A pillow insert should generally be 2 to 4 inches larger than the cover. For standard throw pillows, 2 inches (like 20×20 for an 18×18 cover) is the most common and reliable rule.
Can I put two inserts in one cover?
Yes, you can use two smaller inserts to achieve fullness. For example, using two 18×18 inserts in one 18×18 cover will create a very firm, overstuffed look. This technique is sometimes used in high-end design for a specific, ultra-plump effect.
Do I need a special insert for an envelope closure cover?
No, the same sizing rules apply. The technique for inserting it might be slightly different, but a 20×20 insert will still give the best result for an 18×18 envelope pillow cover.
Special Situations and Styling Advice
Outdoor Pillows
For outdoor 18×18 pillow covers, always use an insert specifically labeled for outdoor use. These are made from quick-drying, mildew-resistant materials. Still, follow the size-up rule—a 20×20 outdoor insert is ideal. Bring inserts indoors during very wet weather to prolong their life.
Floor Pillows and Large Seating
If your 18×18 pillow is used as a floor cushion or for extra seating, opt for a firmer, high-density insert. A 20×20 memory foam or extra-firm fiberfill will hold up better to weight and frequent use, maintaining its shape longer than a soft down blend.
Mixing and Matching Sizes
For a dynamic sofa arrangement, mix your 18×18 pillows with other sizes. The sizing rule applies universally: always choose an insert 2 inches larger. So, a 22×22 cover gets a 24×24 insert. This consistency in fullness ties your different pillow sizes together visually.
Remember, the goal is to create a cohesive and inviting space. A well-stuffed pillow looks cared for and intentional, adding comfort and style to any room. Taking the time to choose the right what size insert for 18×18 pillow cover makes a noticeable difference in your final decor. With the right 20×20 insert and a bit of fluffing, your pillows will look fantastic for years to come.