Is stacking two pillows bad for side sleepers?

It is a workaround for a pillow that is too low, and it comes with a cost. Two stacked pillows compress unevenly, the top one slides during the night, and the combined surface tends to be softer than a single firm pillow of the same height, so your head sinks through it by morning. If two pillows feel right, that tells you the loft you need — buy one pillow of that height and firmness instead. General comfort guidance, not medical advice.

Do side sleepers need a pillow between the knees?

Most find it helps. Side sleeping lets the upper leg drop forward and down, which rotates the pelvis, and a pillow between the knees keeps the thighs roughly parallel. Any firm pillow works; a dedicated contoured knee pillow just stays put better. A folded blanket is a legitimate zero-cost trial — if a week with something between the knees makes a difference, buy the proper version. Persistent hip or back pain is a clinician question rather than a bedding one.

Should a side sleeper hug a body pillow?

It is optional and it does two useful things: it stops the upper shoulder rolling forward, and it supports the upper arm so the shoulder is not carrying its own weight all night. A full body pillow replaces the knee pillow because it runs from arms to knees. The downsides are bulk, heat and, for couples, the space it takes. Try a spare standard pillow hugged to the chest before buying a 54 inch body pillow.

Does the number of pillows change on a soft mattress?

The number stays at one, but the height changes. A soft mattress or a thick topper lets the shoulder sink into the surface, which closes part of the gap the pillow was filling, so the same person needs a lower pillow on a plush bed than on a firm one. If you add a 3 inch topper and start waking with a stiff neck, the pillow that was right before is now too tall — that is the usual cause and it is easy to miss.

How Many Pillows Should a Side Sleeper Use? One, Plus a

Q: How high should a side sleeper pillow be?

Enough to fill the gap between the mattress and the side of your head, which for most adults is 4 to 6 inches of loft under load. Measure it: lie on your side without a pillow and have someone measure from the mattress surface to the outside of your ear. That is your target, and a pillow needs to be somewhat taller than that unloaded because it compresses. Broad shoulders need more, a soft mattress needs less because the shoulder sinks in.

Written & researched by Derek Holt Home & Appliances Editor

Updated October 2026

Golden-hour view of a person smoothing a duvet across a made bed

Affiliate Disclosure

Some links on this page are affiliate links. As an Amazon Associate, we earn from qualifying purchases — at no extra cost to you. We do not buy, test, or physically handle the products we cover; our rankings come from aggregated owner reviews, ratings and expert consensus. Commissions never change our verdicts. How we rank · full disclosure.

One head pillow, plus one between the knees. The head pillow should have 4 to 6 inches of loft under load — enough to fill the gap between the mattress and the side of your head so the neck stays level with the spine rather than bending down toward the mattress. The knee pillow keeps the upper leg from dropping forward and rotating the pelvis. That is the whole functional set. Extra pillows behind the back or hugged in front are comfort preferences, not requirements, and stacking two head pillows usually makes things worse.

How do you find the right loft?

Measure the gap rather than guessing. Lie on your side on the mattress with no pillow and have someone measure from the mattress surface to the outside of your ear. That distance is what the pillow has to fill. For most adults it lands between 4 and 6 inches, and broad-shouldered people can need 6 to 7.

Then account for compression. A pillow labeled 6 inches will compress to 4 or 5 under head weight depending on fill and firmness, so buy slightly taller than your gap and firmer rather than softer — a soft pillow at the right height collapses to the wrong height by 2am. The mattress matters too: a plush surface or a thick topper lets the shoulder sink, which reduces the gap and means you need less pillow. The detail is in best pillow height for side sleepers.

Three-quarter view of a person smoothing a duvet across a made bed, in warm evening lamplight

Which pillows do what?

Pillow	Job	Necessary?	Typical cost
Head pillow, 4–6 in loft, medium-firm	Keeps neck level with spine	Yes	$40–$110
Knee pillow	Stops the pelvis rotating forward	Strongly recommended	$20–$45
Body pillow	Supports upper arm and knees together	Optional; replaces the knee pillow	$40–$90
Small pillow hugged to chest	Stops the top shoulder rolling forward	Optional	Use a spare
Pillow behind the back	Stops rolling onto the back	Only if you roll and it bothers you	Use a spare
Second stacked head pillow	Compensates for a pillow that is too low	No — buy the right pillow instead	—

Over-the-shoulder view of a person smoothing a duvet across a made bed, in bright midday sun

Why is stacking two pillows a bad substitute?

Three reasons, and they compound. Stacked pillows compress unevenly, so the effective height at 6am is not the height you fell asleep on. They slide, because there is nothing holding the top one in place once you move. And the combined surface is softer than a single pillow of equal height, since you are now sinking through two compressible layers instead of one supported one.

The useful information in stacking is diagnostic. If two pillows feel right, measure the stack under your head and buy a single pillow at that loft with a firmer fill. That converts an unstable arrangement into a stable one at no extra cost.

Low-angle view of a person smoothing a duvet across a made bed, in warm late-afternoon light

Why does the knee pillow matter?

Because gravity acts on the upper leg. On your side, the top leg wants to fall forward and down across the bottom one, which rolls the pelvis forward and twists the lower back for the whole night. A pillow between the knees holds the thighs roughly parallel and keeps hips, pelvis and shoulders in one plane.

Any firm pillow does the job. A contoured knee pillow with a strap stays put better; a folded blanket is a free way to test whether it makes a difference for you before spending anything. This is general comfort guidance and not medical advice — recurring hip, knee or lower back pain is worth raising with a clinician rather than resolving through pillow choice alone.

Does fill type change how many you need?

It changes how well one pillow holds its height, which is the same thing in practice. Solid memory foam and latex hold loft consistently through the night, which is why they are the common recommendation for side sleepers. Down and polyester compress and need repeated fluffing, which is exactly how people end up stacking. Shredded memory foam sits in between and has the advantage of being adjustable — remove or add fill until the loft matches your measured gap.

Pillows also lose loft as they age, and a pillow that used to be right and now needs help is simply finished; the fold test and replacement intervals are in how often to replace pillows. Our side sleeper pillow picks rank on how owners describe loft retention after a year, and if the mattress under it is part of the problem, mattress firmness by sleeping position covers the surface underneath.

We never buy, test or physically handle the products we rank. Recommendations come from aggregated owner reviews, star ratings, review volume and expert consensus — see how we rank.

More from this hub: Bedding & Sleep · Toppers for back pain · Topper thickness · How we rank

How Many Pillows Should a Side Sleeper Use?