Finding the right size insert for an 18×18 pillow cover is a common question for anyone refreshing their home decor. Getting the fit correct makes all the difference between a plump, inviting pillow and one that looks sloppy or overstuffed. This guide will walk you through everything you need to know to achieve that perfect, professional look every time.
What Size Insert For 18×18 Pillow Cover
The simple answer is that you typically need an insert that is 2 inches larger than your cover. For an 18×18 inch pillow cover, you should use a 20×20 inch pillow insert. This rule ensures the cover is fully filled out, creating crisp corners and a luxuriously plump appearance without any sagging fabric.
Why go bigger? Pillow inserts compress over time and with washing. A larger insert guarantees your cover always looks full. Using an 18×18 insert in an 18×18 cover will often result in a flat, underfilled look because there’s no extra material to fill the seams and corners completely.
Why the 2-Inch Rule is the Standard
This isn’t just a random suggestion; it’s a standard practice in interior design and upholstery. Here’s why it works so well:
- Combats Compression: Feather, down, and poly-fill inserts naturally compact with use. Starting bigger means they can settle and still look great.
- Creates Structure: The extra size forces the insert to push into every corner of the cover, giving it a defined, structured shape.
- Allows for Seam Allowance: The listed cover size is the finished exterior size. The interior space is slightly smaller due to fabric taken up by seams. A bigger insert accounts for this.
Considering Different Insert Fill Materials
The “20×20 rule” is perfect for most fills, but you can make slight adjustments based on the material inside your insert. The density of the fill plays a big role.
Down & Feather Inserts
For a 18×18 cover, a 20×20 down insert is ideal. Down is very compressible, so you need the extra size. For a super-plump, luxury hotel look, some people even size up to a 22×22 insert, though this creates a very full, firm result.
Polyester Fiberfill (Standard Poly-fill)
A 20×20 poly-fill insert is your best bet. These holds their shape reasonably well but will still flatten a bit. The 2-inch oversize compensates perfectly for this.
Memory Foam or Shredded Foam
These are much denser and less compressible. For an 18×18 cover, you might get away with a 19×19 or even an 18×18 insert if you prefer a firmer, more structured bolster-like pillow. However, a 20×20 will still give the fullest look.
Step-by-Step: How to Insert and Fluff Your Pillow
Putting the insert in the cover the right way ensures you don’t strain the seams and helps with fluffing.
- Turn your pillow cover inside out and lay it flat.
- Place your 20×20 insert on top of the cover, aligning the corners as best you can.
- Start rolling the insert into the cover, like you’re rolling a sleeping bag. Keep going until the entire insert is rolled up inside the cover fabric.
- Reach inside and find the two far corners of the insert. Grab them through the cover fabric.
- Now, gently but firmly pull the cover right-side out over the rolled insert. The cover will turn right-side out as you pull.
- Once the cover is on, give the pillow a good shake and punch the corners to settle the insert fully into place.
- Finally, fluff it by grabbing opposite ends and giving it a good smack and shake. Rotate and repeat.
What If You Already Have an 18×18 Insert?
Don’t worry if you already have an 18×18 insert. You can still use it with your 18×18 cover, but you’ll need to manage expectations. It will have a more casual, relaxed look. To improve the fit, make sure you fluff it vigorously before inserting. You can also add extra fill. Some craft stores sell bags of polyester fiberfill; you can open a seam on your insert and add a handful or two to boost its volume before sewing it closed again.
Special Cases and Adjustments
Not every situation is textbook. Here are some common scenarios and how to handle them.
For a Super-Firm, Upholstered Look
If you want an extremely tight, firm pillow like on a formal sofa, consider a 22×22 insert. This is especially effective with down-alternative or poly-fill inserts in a tight, non-stretch cover like linen or canvas. Be aware that it can be tricky to get the insert in, and you might put slight stress on the cover’s zipper or envelope closure.
For a Soft, Slouchy Look
For a casual, slouchy vibe on a bed or reading nook, an 18×18 insert in an 18×18 cover can actually work. The key is to use a cover made from a soft, drapey fabric like a loose knit or washed velvet, and an insert that’s not overstuffed to begin with.
When Your Cover Has a Lot of Stretch
Stretchy materials, like some jersey knits or spandex blends, will conform to the insert. In this case, you could use either an 18×18 or a 20×20. The 20×20 will stretch the fabric more for a smoother look, while the 18×18 will have more gathered texture.
Measuring Your Pillow Cover Correctly
Before you buy anything, double-check your cover’s true size. A seamstress’s measuring tape is the best tool.
- Lay the cover flat and smooth it out.
- Measure from seam to seam across the front, not including any flange or trim. Do this for both width and height.
- If it’s a envelope closure or zipper closure, make sure you’re measuring the front panel only.
- Remember, if the cover is labeled 18×18, it should measure close to that when laid flat. If it’s significantly smaller, you might need to adjust your insert size down a bit.
Buying Tips for Pillow Inserts
Not all inserts are created equal. Here’s what to look for when shopping for your 20×20 insert.
- Construction: Look for “baffle box” or “gusseted” construction. This means there are internal fabric walls that keep the fill evenly distributed, preventing clumping and creating a nicer shape.
- Fill Power (for down): Higher fill power (e.g., 600, 800) means better loft and fluffiness with less weight.
- Fabric Shell: A tight, cotton shell is standard and prevents feathers from poking through. For down alternative, a polyester shell is common.
- Washability: Many inserts, especially down alternative ones, are machine washable. Check the label if this is important to you.
DIY: Making Your Own 18×18 Pillow Cover
If you’re making a custom cover, you need to account for the insert size from the start. Here’s a quick fabric cutting guide for a simple envelope-back cover meant for a 20×20 insert.
- Cut your front panel: Cut one square of fabric to 21×21 inches. This gives you a 1/2-inch seam allowance on all sides.
- Cut your back panels: Cut two rectangles for the overlapping back. For an 18×18 finished cover, cut each to 21 inches tall by 14 inches wide. (The width can vary based on how much overlap you want).
- Sew a hem on one long edge of each back piece.
- Layer the pieces: Place the front piece right-side up. Lay the two back pieces right-side down on top, with their hemmed edges overlapping in the center.
- Pin and sew all the way around the square with a 1/2-inch seam allowance.
- Clip the corners, turn it right-side out, press, and insert your pillow!
Common Mistakes to Avoid
- Using the Same Size: The biggest mistake is using an 18×18 insert. It almost always looks underfilled.
- Not Fluffing Regularly: Pillows need maintence. Give them a good fluff and shake every few days to redistribute the fill and maintain their shape.
- Choosing a Cheap, Low-Fill Insert: A bargain insert often has thin, lumpy fill that won’t fill out the cover properly, even at the correct size. Invest in a quality insert; it makes a huge difference.
- Forgetting to Check Closure Type: A cover with a simple envelope closure might need a slightly fuller insert to keep it from gapping open, compared to a zipper closure.
FAQ Section
What size pillow form for 18×18 cover?
A 20×20 inch pillow form is the recommended size for an 18×18 cover. This ensures a full, plump appearance.
Can I use a 18×18 pillow in a 18×18 cover?
You can, but it will likely look flat and underfilled. For the best results, it’s better to size up to a 20×20 insert.
How much bigger should a pillow insert be?
The general rule is to choose a pillow insert that is 2 to 4 inches larger than the cover. For standard decor pillows, 2 inches larger is the most common and effective sizing.
What is the best fill for an 18×18 pillow?
Down alternative (polyester clusters) is a popular choice for its plush feel, easy care, and affordability. Feather and down blends offer a luxurious, moldable feel but require more fluffing. The “best” fill depends on your preference for firmness, allergy concerns, and budget.
Final Tips for Perfect Pillows
Remember that the goal is to achieve a look you love. Don’t be afraid to experiment slightly. If a 20×20 feels too firm in a particular cover, look for an insert with a less dense fill. If it’s not full enough, try the next size up. Always give your new pillow a good 24-hour fluffing period after taking it out of the packaging; inserts need time to expand to their full size.
Keeping your pillows fresh is also key. Use pillow protectors under your decorative covers, especially if they are light-colored, to protect the insert from dust and stains. This extends the life of both the insert and the cover. With the right 20×20 insert, your 18×18 pillow covers will look polished, inviting, and exactly as you envisioned them in your space.