If you sleep on your side, you probably have a nightly ritual. You fold your pillow in half. Or you stack a second one on top. Or you shove your arm underneath to prop your head up, and wake with pins and needles in your hand. In the morning, one side of your neck is tight, maybe your shoulder too.
Side sleeping is the most common position, and it's generally a good one for your neck. But it has the narrowest margin for error when it comes to pillow height.
Quick answer: Side sleepers need a pillow tall and firm enough to fill the space between the ear and the outer edge of the shoulder, so the head stays in line with the spine. Too low and your head drops toward the mattress; too high and it tilts up. People with broader shoulders need more height. An adjustable pillow, like a water pillow filled to the firm end (about 4–5 L), makes it easy to match your exact gap.
Why side sleepers have it the hardest
When you lie on your back, the distance between your head and the mattress is small. When you lie on your side, your shoulder lifts your whole upper body, creating a gap of roughly 10–15 cm (4–6 inches) for most adults, sometimes more. That gap has to be filled by your pillow, and it has to stay filled all night.
The problem is that most pillows:
- Start too low. Standard pillows are often made for back sleepers.
- Get lower overnight. Fibre and feathers migrate away from under your head. By 3 a.m. the height you started with has shrunk.
- Are too squishy at the centre. Your head is heaviest at one point, which is exactly where soft fill compresses most.
Signs your pillow is too low
- Your head tilts down toward the mattress (your bottom ear is closer to your shoulder).
- You wake with your arm or hand under the pillow, and maybe a numb hand.
- The top side of your neck feels stretched or achy.
- You keep folding the pillow in half.
Signs your pillow is too high
- Your head tilts up toward the ceiling.
- The bottom side of your neck (the side touching the pillow) feels compressed or sore.
- Your top shoulder feels hunched forward.
Find your height: the 2-minute mirror test
- Stand sideways in front of a mirror with your back straight.
- Measure from the side of your neck (just below your ear) to the outer edge of your shoulder. That's roughly the gap your pillow needs to fill when compressed.
- Lie on your side on your pillow, and have someone take a photo from behind or the front.
- Check: does a line from the middle of your forehead through your nose and chin continue straight down your breastbone? If yes, you've found your height.
Don't forget your mattress
A softer mattress lets your shoulder sink further, so you need less pillow height. A firm mattress keeps your shoulder higher, so you need more. It's one reason a pillow that worked at home feels wrong in a hotel.
Side sleeper tips that help your neck
- Tuck the pillow into your neck. Pull the bottom edge of the pillow snugly into the space between your shoulder and jaw, so it supports your neck, not just your head.
- Hug a second pillow. It stops your top shoulder from rolling forward, which can pull on your neck.
- Put a pillow between your knees. It keeps your hips and lower back level, which helps your whole spine line up.
- Switch sides now and then. Spending all night on one side can make one side of your neck work harder.
Why water pillows suit side sleepers
Side sleepers usually need the firmest setting of any position. With the Mediflow Water Pillow you fill to your own shoulder gap, typically 4–5 L for side sleeping, and adjust by half a litre until your head is level. Because water can't be compressed, that height holds through the night instead of sagging by morning. And when you roll onto your back, the water shifts and reshapes under you.
In a randomized study led by researchers at Johns Hopkins, people with neck pain reported less morning pain and better sleep quality on a water-based pillow than on their usual pillow (Lavin et al., 1997).
FAQ
What pillow height is best for side sleepers? One that fills the gap between your ear and shoulder edge, often 10–15 cm (4–6 inches) once compressed. Broad shoulders or a firm mattress mean you need more.
Why does my shoulder hurt when I sleep on my side? A pillow that's too low can make you sink your shoulder or tuck your arm underneath. A supportive pillow and a medium mattress can help. If shoulder pain persists, check with a physiotherapist.
Should side sleepers use a firm pillow? Generally, yes: firm enough that it doesn't collapse under the weight of your head through the night.
Stop folding your pillow in half. Shop the Mediflow Water Pillow and set the exact height your shoulders need.
This article is for general information and isn't medical advice. If you have ongoing or severe neck pain, please talk to a healthcare professional.