Finding the perfect pillow plumpness starts with knowing what size pillow insert for 18×18 cover. It’s the key to a professional, polished look for your throw pillows, whether you’re refreshing your sofa or finishing a new bed. Get this detail right, and your decor instantly looks more expensive and intentional. Get it wrong, and you’ll be left with a pillow that’s either too limp or frustratingly overstuffed.
This guide will walk you through everything you need to know. We’ll cover the simple rule of thumb, when to break it, and how to choose the right fill material for your needs. You’ll be a pillow-pro in no time.
What Size Pillow Insert For 18×18 Cover
The golden rule for a perfect pillow fit is to choose an insert that is 2 inches larger than your cover. Therefore, for an 18×18 inch pillow cover, you should typically select a 20×20 inch pillow insert. This ensures the cover is fully filled out with no sagging or empty corners, creating a luxuriously plump appearance.
Why does this work? Pillow covers are designed with a seam allowance, which slightly reduces the interior space. A larger insert compensates for this, filling every part of the cover. It also accounts for the natural compression of the insert’s filling once it’s inside the cover.
The Simple Sizing Formula Explained
Let’s break down the math so you can apply it to any pillow.
- Cover Size: 18 inches by 18 inches.
- Insert Size: Add 2 inches to each dimension (18 + 2 = 20).
- Result: Use a 20×20 inch insert.
This 2-inch rule is standard across the home decor and sewing industries. It’s a reliable starting point for most common pillow types, from simple square throws to lumbar styles. If you’ve ever wondered why store-bought pillows look so full, this is their secret.
When to Deviate from the 2-Inch Rule
While the 20×20 insert is the standard recommendation, the perfect plumpness is sometimes subjective. Here are scenarios where you might adjust the size.
For a Softer, More Casual Look
If you prefer a slouchy, relaxed pillow, you might opt for an insert that matches the cover size exactly (18×18) or is only 1 inch larger (19×19). This works well with knit or very stretchy fabric covers that will form around the insert without tension.
For an Ultra-Firm, Structured Look
Some decor styles, like very modern or formal settings, call for a crisp, geometric pillow. In these cases, you could even try an insert that is 21×21 inches. Be cautious with this, as it can put strain on the cover’s seams if the fabric isn’t flexible.
Considering the Fabric Thickness
A thick, upholstery-weight fabric (like velvet or heavy linen) takes up more internal space than a thin cotton. For thicker covers, sticking to the 20×20 is crucial. For very thin, silky covers, you might find a 20×20 insert gives you the perfect amount of fullness without being forced.
Step-by-Step: How to Insert Your Pillow Correctly
Getting the insert into the cover properly makes a big difference in the final look.
- Fluff the Insert First: Before you start, shake and punch your pillow insert to evenly distribute the filling. This is especially important for down or feather blends.
- Turn the Cover Inside Out: Reach into the cover and grab the inner corner of the insert pocket (the opposite corner from the opening).
- Pull the Cover Over: Using that inner corner, pull the cover over the insert, almost like putting on a sock. This technique prevents the insert from getting caught and bunching up.
- Adjust and Smooth: Once the insert is fully inside, gently shake the pillow and push the filling into all four corners from the outside.
- Close It Up: Secure the closure (whether it’s a zipper, envelope, or buttons). Give the pillow a final plump and smoothing.
Choosing the Right Fill Material
The insert’s size is half the battle; the fill material determines the feel, shape, and maintenance. Here are the most common options.
Down and Feather Blends
This is the gold standard for a luxurious, moldable pillow. It offers superior softness and the ability to fluff back into shape easily.
- Pros: Extremely plush, durable, molds to your preference.
- Cons: Requires regular fluffing, can trigger allergies, is often the most expensive option.
- Best For: Living room throw pillows where luxury and comfort are the priority.
Polyester Fiberfill (Standard)
A very popular, affordable, and hypoallergenic choice. It holds its shape reasonably well but can flatten over time.
- Pros: Budget-friendly, hypoallergenic, machine washable, holds shape decently.
- Cons: Can look lumpy with low quality fills, may flatten and need replacing sooner.
- Best For: Kids’ rooms, seasonal decor, or anyone with allergies.
Memory Foam or Shredded Foam
Offers excellent support and a very structured, firm shape. It doesn’t require fluffing.
- Pros: Provides firm support, maintains its shape perfectly, good for lumbar pillows.
- Cons: Less soft and malleable, can be heavier, sometimes has an initial odor.
- Best For: Pillows used for actual back support, like on an office chair or reading nook.
Down Alternative (Microfiber)
Seeks to mimic the feel of down with synthetic materials. It’s usually very soft and hypoallergenic.
- Pros: Soft and plush, hypoallergenic, often machine washable, more affordable than down.
- Cons: May clump more than down over time and with washing.
- Best For: Those who want a down-like feel without the allergens or higher price tag.
Common Pillow Sizing Mistakes to Avoid
Even with the right size insert, other errors can ruin your pillow’s look.
- Not Fluffing First: Inserting a flat, packed-down pillow will lead to uneven filling and poor shape.
- Ignoring the Fill Power: For down inserts, a higher fill power means more loft with less weight. A 20×20 with low fill power may still look flat.
- Forgetting to Adjust: After inserting, you must manually push filling into the corners. Don’t just zip it up and assume it will settle perfectly.
- Using a Worn-Out Insert: Old inserts lose their volume. If your new cover doesn’t look full even with a larger insert, the insert itself might be the problem and need replacing.
Care and Maintenance for Lasting Fullness
To keep your 18×18 cover and its insert looking great, follow these tips.
- Fluff Regularly: Give your pillows a good shake and punch every few days to redistribute the filling and maintain loft.
- Wash According to Label: Most inserts (except down) can be machine washed on gentle. Always use a delicate detergent and dry thoroughly on low heat with tennis balls or dryer balls to break up clumps.
- Store Properly: When storing seasonal pillows, avoid compressing them for long periods. Use a breathable storage bag instead of vacuum-sealing, which can permanently damage the fill’s ability to rebound.
- Spot Clean Covers: To minimize wear, spot clean your pillow covers when possible instead of washing the entire pillow every time.
FAQ: Your Pillow Insert Questions Answered
Q: Can I use an 18×18 insert in an 18×18 cover?
A: You can, but the result will likely be underfilled and look a bit sloppy. The corners may not be sharp, and the pillow might appear flat. It’s better to size up for a fuller look.
Q: My 20×20 insert feels too tight in the cover. What’s wrong?
A: The fabric might have very little stretch, or the insert could be exceptionally firm. You can try a 19×19 insert, or gently massage and fluff the 20×20 insert to soften it before trying again. Sometimes, after a few days, the insert will relax and fit better.
Q: How do I measure my pillow insert accurately?
A: Lay the insert flat on a surface. Use a measuring tape to measure from seam to seam across the center. Don’t measure just the fluffy outer edges, as this can give an inaccurate reading.
Q: Is a down or feather insert better than polyester?
A: “Better” depends on your goals. Down/feather offers a premium, moldable luxury feel but requires care and is more expensive. Polyester is low-maintenance, hypoallergenic, and affordable. Choose based on your budget, desired feel, and how much upkeep your willing to do.
Q: Where can I buy a 20×20 pillow insert?
A: They are widely available at home goods stores, craft stores like Joann or Michaels, online retailers like Amazon, and from specialty bedding websites. Always check the dimensions in the product description, as labeling can sometimes be vague.
Q: Can I make my own pillow insert?
A> Absolutely. If you sew, you can create a simple envelope-style cover and stuff it with loose polyester fiberfill or shredded foam. Just be sure to pack the filling very densely, as it will settle over time. Making your own allows for complete customization of firmness.
Troubleshooting Specific Problems
Problem: Lumpy or Uneven Pillow
Solution: This is often caused by low-quality fiberfill or an old down insert where the feathers have broken. For fiberfill, try washing and drying the insert with dryer balls to redistribute the filling. For a lumpy down insert, you may need to carefully open a seam, add more fill, and restitch it.
Problem: Pillow Won’t Stay Plump
Solution: The insert is likely underfilled or has lost its loft. The easiest fix is to add more filling. For a fiberfill insert, you can open the closure, add a bag of extra polyester stuffing, and mix it in. For a persistent problem, replacing the insert is the best long-term solution.
Problem: Corners Aren’t Filled
Solution: This is usually an adjustment issue. Before closing the cover, reach inside and physically push filling from the center of the insert out towards each corner. You need to manually shape it. If there’s genuinely not enough filling to reach the corners, the insert is too small.
Choosing the correct pillow insert size is a small detail with a huge visual impact. By remembering that a 20×20 inch insert is the ideal partner for your 18×18 inch cover, you guarantee a professional, cozy, and inviting result. Pair that with the right fill material for your lifestyle, and your pillows will not only look fantastic but feel comfortable for years to come. Now you can confidently shop for or make inserts, knowing exactly how to achieve that perfect, plump pillow look you see in magazine spreads. It really is that simple.