For side sleepers

Before you buy the butterfly pillow, check one number

Every pillow says it's for side sleepers. Few tell you the height. Too high or too low, that's the part to check, not the shape. Here's a free test you can do tonight with a ruler, and my honest take on whether the Derila Ergo is the right height for you.

By Wally. I'm not a doctor. I'm an affiliate. Updated October 28, 2026.

The video includes short clips from creators Derila paid. Each one is labeled on screen.

Affiliate link. Opens Derila's page.

Your closet of pillows isn't your fault

Tried so many pillows you've lost count? Packed the ones that didn't work into the closet? You weren't doing it wrong.

I think most people shop for pillows by soft or firm. The number they skip is height.

Look at what people do at night instead. They stack two pillows. They fold one in half. They sleep with an arm under it. I think those are all ways of fixing the same thing: height.

The shoulder gap

When you lie on your side, your shoulder lifts your head off the mattress. A pillow has to fill that gap. I call it the shoulder gap.

A small study published in 2025 had nine side sleepers try four pillow heights. The researchers used each person's shoulder width to work out the height that lined the neck up best. ¹

The test below is a simple home version of that idea. It isn't the study's method.

And pillows sag. The Sleep Foundation says to replace memory foam ones every two to three years. ² So if you can't remember when you bought yours, that's your reason to check this week.

The free test (about two minutes)

1. Find your shoulder number. Take a ruler. Measure across the top of your shoulder, from the side of your neck to the edge. On your side, that's roughly how high your head sits off the mattress.
2. Measure your pillow, squashed. Press your pillow down about as hard as your head would, and measure how tall it is.
3. Compare. If your pillow is a lot thinner than your shoulder number, it probably isn't filling the gap.
4. Try the towel test tonight. Fold a towel and put it under your pillow to raise it. If that's more comfortable, a taller pillow may be worth it. A towel is fine for a test, but it can shift around.

The honest part

The Ergo's number

This is where I earn my commission, so judge for yourself.

Derila lists the Ergo at about 4.7 inches, before your head is on it. ⁴ Memory foam sinks some, so it will sit lower.

If your pressed-down pillow is far under that, the Ergo is a lot taller than what you have. If it's close, you may not need a new pillow.

And if your shoulder number is well over 4.7 inches, this one may not be tall enough for you either.

Why not just buy a thicker regular pillow?

You can. If it fills your gap, that works too.

Here's what Derila built into this one, from their own guide: ⁴

• A front curve that Derila says rests against the side of your neck.
• A cutout for your arm.
• A zip cover you can take off and machine wash.
• It ships vacuum packed. Derila says to give it 6 to 8 hours to puff back up.
• Size listed as 21.2 by 14.1 by 4.7 inches.

In late October 2026, one was about $60 on their page. Prices change, so check theirs.

You get 60 days to return it in usable condition. They don't refund shipping. ⁵

Who should skip it

I read buyer reviews before writing this. People complain about the Ergo's height both ways. Some say it's too low for their shoulders. Others say it's too high. That's why I'd do the ruler test first. This pillow isn't for everyone.

• You want a soft pillow. It's firm memory foam. Reviewers split on that, and many say it took a few nights to get used to.
• Your shoulder number is well over 4.7 inches. It may not be tall enough.
• You expect a big pillow. It's 21.2 by 14.1 inches, so picture that size before you order.
• You're shopping for snoring help. I make no snoring or sleep claims. This review is only about fit.

Which one are you?

Again, I get paid if you buy through my link, so do the test first.