Understanding Pillow Insert Sizes for 18×18 Pillow Covers
When selecting the correct size insert for an 18×18 pillow cover, a general rule of thumb is to choose an insert that is 2 inches larger than the cover size. For an 18×18 pillow cover, a 20×20 inch insert is typically recommended to ensure your pillow looks full and plush. This might seem counterintuitive, but the extra 2 inches of the insert will fill out the cover properly, providing a nice, tight fit and a plump appearance.
Why Choose a Larger Insert?
The reasoning behind choosing an insert that is larger than your pillow cover is to give the pillow a more luxurious and cozy feel. If you were to select an insert that is the exact size of your pillow cover, the pillow could look flat and underfilled. By using an oversized insert, you can ensure that the corners and edges of the pillow cover are adequately filled out, which can have a significant impact on the pillow’s overall look and comfort.
The fill of the insert also plays a role in how your pillow will appear. Down and feather inserts often require more generous sizing because they can be more compressible, while a firmer foam or synthetic fill may not need quite as much sizing up to achieve the desired fullness.
Types of Pillow Inserts
Before diving deeper into sizing, let’s discuss the types of pillow inserts available, as this will influence the level of plushness and the sizing you might want.
Our Top 5 Pillow Picks
Updated September 2026MFWW Cervical Contour Memory Foam Pillow
Best for neck pain. A dual-height ergonomic contour cradles your head and supports the neck, for back and side sleepers.
- Contour memory foam
- Dual-height design
- Cool breathable cover
Cooling Shredded Memory Foam Pillows, Standard, 2-Pack
Best value pair. Shredded foam you can adjust to your loft, with a cool-gel feel and no solid-block heat. Two pillows in one box.
- Adjustable shredded foam
- Cool gel
- Hypoallergenic
- Standard 2-pack
Cooling Shredded Memory Foam Pillows, Queen, Set of 4
Best for the whole household. The same adjustable cooling foam in queen size, four to a set, so every bed in the house gets an upgrade.
- Adjustable shredded foam
- Cool gel
- Hypoallergenic
- Queen set of 4
Utopia Bedding Hotel Pillows, Queen, Set of 4
Best hotel-style set. Plush, cooling pillows made to suit side, back and stomach sleepers alike. A safe pick for guest rooms.
- Queen set of 4
- Cooling
- All sleep positions
- Hotel style
Zalmureta Goose Feather & Down Pillows, Queen, Set of 2
Best luxury pick. A three-chamber goose feather and down fill wrapped in a 100% cotton shell, for that five-star-hotel feel at home.
- Goose feather & down
- 3-chamber design
- 100% cotton shell
- Queen 2-pack
- Down and Feather Inserts: These inserts are known for their softness and pliability. They’re often considered the luxe option and can be quite comfortable. They can be fluffed and will need a more substantial size increase for a full look.
- Polyester Fiberfill Inserts: A common choice for those with allergies to down feathers, these are usually less expensive and can range from very soft to very firm, depending on the filling amount and quality.
- Foam Inserts: If you prefer a firmer pillow that holds its shape well, foam inserts might be your choice. They also tend to keep their shape over time without much fluffing required.
- Microbead Inserts: Microbead pillows offer support and can be a good choice for those looking for a pillow with a bit more structure but still comfortable and flexible.
Measuring Your Pillow Cover
To get the best fit possible, it’s essential to measure your pillow cover accurately. Lay the cover flat and measure from one side seam to the other. Ensure that you are not stretching the fabric as you measure. Use a firm tape measure and go from edge to edge. Note that some pillow covers might shrink slightly after washing, so keep this in mind if you’re measuring a cover that has been laundered.
Custom and Odd-Sized Covers
While the 20×20 inch insert size works well for standard 18×18 covers, you may occasionally come across a handcrafted or odd-sized pillow cover. For these, you may still apply the same principle of adding 2 inches, but you may also need to consider having a custom insert made or adjust the fill of an existing insert for a perfect fit.
Adjusting the Firmness of Your Pillow
What if you have an existing 20×20 inch insert that doesn’t feel quite right in your 18×18 cover? You can adjust the firmness of your pillow by adding extra stuffing if it has a zippered cover, or by removing some of the fill if it’s too plump. This is particularly feasible with down, feather, and polyester fiberfill inserts.
Factors to Consider When Selecting Your Insert
When you’re in the market for a new pillow insert, consider the following factors to ensure you make the best choice for comfort and appearance:
Fabric Type
- Natural Fabrics: If your pillow cover is made of a natural fabric, such as cotton or linen, it may benefit from a down or feather insert for breathability and softness.
- Synthetic Fabrics: A synthetic cover might pair well with a polyester or foam insert, particularly if the fabric doesn’t stretch.
Intended Use
Whether the pillow will be used for decoration, support, or sleeping can guide your choice. Decorative pillows can be overstuffed for a full look, while a pillow for sleeping may need to precisely fit your comfort level.
Allergies
Always consider allergies when selecting pillow fill materials. Alternative down or hypoallergenic materials can be a safe choice for those with sensitivities.
Easy Maintenance
Look for inserts that are easy to clean or maintain. Some inserts can be laundered at home, while others might require professional cleaning.
Environmental Impact
For the environmentally conscious, consider the sustainability of the pillow fill. Natural down may not always be the most ethical choice; however, there are certified sustainable down options available. Similarly, there are eco-friendly synthetic fills made from recycled materials.
Durability
Consider the longevity of the insert. High-quality down inserts can last for many years if properly cared for, while cheaper synthetic inserts might flatten or lump after repeated use.
Finishing Thoughts
Choosing the right size insert for your pillow cover is a key detail that can make a significant difference in the look and feel of your pillow. While the standard recommendation for an 18×18 pillow cover is a 20×20 inch insert, it’s essential to consider the type of fill, cover fabric, and your personal preferences for firmness and usage to get the perfect pillow setup for your space. With the right insert, your pillow can be the perfect combination of form and function, adding both style and comfort to your living areas. Remember that the beauty of pillows is that they are versatile and can always be adjusted to meet your needs. Enjoy the process of creating a cozy ambiance with the perfect pillow choices for your home.
