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You’ve bought your pillow cover, but, now what?! To help it live its best pillow life possible, I really want to help you easily determine what size inserts you should buy for your pillow covers! It can be a confusing world, with sizing nuances from every manufacturer, knowing what to size up on, how much, etc. I’m so excited to give you my tried and true recommendations! 

Design: Eye for Pretty || Photo: Amy Bartlam


The one thing you ALWAYS want to do, is size UP on your insert size.  Which means that whatever size your pillow cover is, you need your insert to be larger than it! As a general rule, the smaller the size of your pillow cover, the less you have to size up on your insert.  And, the larger the size of your pillow cover, the more you are going to want to size up. 


Once you’ve found the perfectly sized insert, you want to make sure that you are putting it into your pillow cover properly.  Otherwise, it is not going to matter how good your insert is!!

Design: Harlowe James || Photo: Torrey Fox


Your preference on the softness or firmness of your pillows will also come into play. I’ve built my recommendations based on a mid point, so if you really love a soft, relaxed look, you may want to shave off an inch or two. And do the opposite for firm, but only add an inch or so. I don’t suggest overfilling your pillow covers too much, you will put more stress on the seams and it could stretch out the fabric over time.


This is a huge factor that also comes into play!! I broke down 5 pillow manufacturers’ inserts HERE if you’d like to see the results! The bottom line is that every manufacturer fill weights are different, and there is unfortunately no “one size fits all.” You can usually get away with a lower fill weight on smaller sizes, as you really won’t notice it as much. But, as you start getting into bigger sizes, you have to find a trusted manufacturer to use, or order a few sizes to see which one is the best fit.

Design: Veneer Designs || Photo: Marisa Vitale

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  • Small Lumbar (11”x19-11”x23”): Size up 1” on your insert size, using a 12”x20” and 12”x24” insert respectively. You could get away with 2” more on the longer side, but I wouldn’t go more than that. I’ve used THIS ONE for 12″x20″ and I am a fan of THIS BRAND that also has a 12″x20″ size.  Check them out for a 12″x24″ size as well!!
  • Medium Lumbar (14”x22”- 15”x23”): Size up 1-2” on your insert size, a 16”x24” down/feather insert usually works well on these sizes.  I use THIS ONE all the time for these sizes.  It is slightly bigger than recommended, but it isn’t filled as much, so it still works!
  • Large Lumbar (13”x34”- 18”x48”): Size up about 2-3” on these, but mainly on the longer side. For example, for a 13”x34” cover, you can use a 14” (sized up 1”) x36” (sized up 2”) insert, HERE. For the large size, I recommend finding a body pillow insert! And if you’re looking to save money on these, I have used poly inserts (like THIS ONE), because they help retain the shape a bit better. The longer the measurement, the more you’ll want to size up on it to provide the best overall fill!

SIZE GUIDE – SQUARES (you can find any of these sizes HERE)

  • Small Square (17”x17” and smaller): Size up 1” for your insert size. For a 17″x17″ size cover, use an 18″x18″ insert.
  • Medium Square (18”x18”-20”x20”): Size up 2” for your insert size. For an 18″x18″ size cover, use a 20″x20″ insert.
  • Large Square (22”x22”- 24”x24”): Size up 2-3” for your insert size. For a 22″x22″ size insert, use a 24″x24″ insert.  I use THESE all the time for my 22″x22″ covers.  While I usually wouldn’t recommend sizing up this much, the fill isn’t has heavy as most manufacturers, so it fills more like a 24″x24″ insert.  You may have to finesse your insert sizing for 22″-24″ square pillow cover sizes, as manufacturer fill weight differences become more noticeable on the larger sizes.  I would err on the side of a larger insert, rather than smaller, when choosing inserts for your 24″x24″ pillow covers (go up 2-4″ depending on your fill preference- soft or firm)!
  • Extra Large Square (26″x26″ and larger): Size up 3-4″ for your insert size

The above guides should really be a fool proof way to plump up your pillows! I’ve referenced down/feather inserts only, because they have more “give” than firmer polyester or down alternative inserts.  While you can still size up on down alternative inserts, I’d lean towards sizing up at a rate of about half of what I’ve given above.

And, if you ever need a suggestion for a size not covered here, please don’t hesitate to contact me!

xx, Monica

P.S. In case you missed it above, I tested 5 manufacturer’s pillow inserts to give you the low down on the best bang for your buck!  You can read more about it HERE!