Best Pillow for Side Sleepers: What to Check Before You Buy
The best pillow for a side sleeper is one whose height fills the gap between the head and the mattress, and that gap depends mainly on shoulder width. No single stock height fits every side sleeper, so check height first, then mattress firmness, then fill and feel.
Key takeaways
- Pillow height is worth checking first. In a pilot EMG study of 15 adults, a pillow height matched to shoulder width produced the lowest neck and shoulder muscle activity during side sleeping (Jiao et al., 2025).
- Mattress firmness changes the gap. A soft mattress lets the shoulder sink, a firm one does not, so the same pillow can fit differently on each.
- A pillow fitted to your measurements takes the guesswork out. A measurement at a provider near you is free at every Pillowise reseller.
What does a side sleeper need from a pillow?
On your side, the shoulder becomes the widest point between your head and the mattress. The pillow has to fill that space. If it is too low, the head tilts toward the mattress. If it is too high, the head tilts away from it. Either way, the neck holds that angle for hours.
The goal is simple: a neck that stays roughly in line with the rest of the spine while you sleep. Most pillow marketing talks about fill and feel. For a side sleeper, the first question is how tall the pillow sits under your head.
Why check pillow height first?
Height is the variable that most directly sets the angle of the neck. In the pilot EMG study mentioned above, researchers measured muscle activity in the trapezius and sternocleidomastoid while people lay on their sides. Activity was lowest, and comfort ratings highest, with a pillow height matched to shoulder width (Jiao et al., 2025). We cover that study in more detail in side sleeping, shoulder width and pillow height.
What the study does not show: it was small, it used a pilot design, and it did not follow people over weeks or months. Studies like it tend to use mostly healthy young adults, and none that we cite tested people with shoulder pain. It supports checking height first. It does not prove that any pillow treats neck or shoulder pain.
How do your mattress and body change the answer?
Two things shift the gap between head and mattress even when shoulder width stays the same.
- Mattress firmness. On a soft mattress, including many memory foam and hybrid models, the shoulder sinks in and the gap shrinks. On a firm mattress, the gap stays larger.
- Body weight. A heavier person sinks deeper into the mattress and may need a lower pillow. Weight is not part of the Pillowise algorithm, which is why a provider checks the position on the pillow and adjusts if needed.
This is also why a pillow that worked well in a hotel or at a friend's house can feel wrong at home. For a broader look at matching a pillow to position and mattress, see how to choose the right pillow based on your sleep position and mattress.
What should you look for when shopping?
Use this order. It keeps the decision simple.
| Step | What to check | Why it matters for side sleepers |
|---|---|---|
| 1. Height | Pillow height compared with your shoulder width | Sets the angle of the neck on your side |
| 2. Mattress | Soft, medium or firm, including memory foam and hybrid | Changes how far the shoulder sinks |
| 3. Fill | How the material compresses and recovers | A pillow that flattens overnight loses its height |
| 4. Cover and care | Removable, washable cover | Easier to keep clean for daily use |
| 5. Return policy | Time to adjust and a way to exchange | A new pillow needs several nights before you can judge it |
Most people shop by step 3 and 4 and hope step 1 works out. Reversing the order is the main change we suggest.
How can you tell your current pillow is the wrong height?
Common signs include waking with a stiff neck, pushing the pillow into a different shape every night, or tucking an arm under it to raise your head. We list more in how to tell if your pillow is the wrong height. These signs are hints, not a diagnosis. Stiffness has many causes, including your mattress, stress and daytime posture.
When will a pillow not help?
A pillow is an adjunct to care, not a treatment. See your own provider if you have any of the following:
- Neck or shoulder pain that persists or keeps getting worse
- Numbness, tingling or weakness in an arm or hand
- Pain after an injury
- Headaches that are new or unusual for you
A well-fitted pillow will not fix a problem that needs an examination.
How does Pillowise approach side sleepers?
A pillow should fit the body, like a shoe size. We take three measurements: shoulder width, neck circumference and neck height. We add your sleeping position, meaning the position in which you fall asleep, and your mattress firmness. If you do not know your firmness, we choose medium. If you are unsure of your position, we choose side.
The Pillowise algorithm combines these five factors and picks one of 7 sizes. Two people with very different bodies can end up with the same size, because the factors are combined. The system indicates the right size for about 95% of people. A provider then checks the position on the pillow and adjusts if needed, for example during pregnancy.
The standard Pillowise pillow measures 22 x 14 in. The core is 100% premium Dutch memory foam, non-toxic and latex-free, made in the Netherlands. The cover is 40% Tencel and 60% polyester, removable and machine washable at 104°F (40°C). You can read what happens during a measurement in what happens in a pillow fitting, and the reasoning behind it in why a fitted pillow.
A new pillow needs time. Give it 7 to 10 days to adjust. If it still does not feel right, you can exchange it for another size or return it for a refund within 30 days of purchase. Return shipping is paid by the customer, and shipping charges are not refunded. There is also a 5-year warranty on material and production faults. If you want to pay with FSA or HSA funds, ask your plan administrator whether a pillow qualifies under your plan.
Find a provider near you
Pillowise is sold only through licensed healthcare providers in the US: chiropractors, physical therapists and licensed massage therapists. It is not sold in retail stores or through a direct consumer webshop. You make an appointment, the provider takes your measurements, and you take the fitted pillow home. The measurement is free at every reseller.
Sleep in another position? See the guides for back sleepers and stomach sleepers.
You can also see how the sizing works on the size page, or browse the FAQ for common questions.
Find a Pillowise provider near you for a free measurement.
Are you a chiropractor, PT or massage therapist? See how to offer fitted pillows in your practice.
Thijs van der Hilst, physiotherapist
Co-founder of Pillowise
