This is a collaborative post.

Side sleeping creates the largest gap of any sleeping position between the side of your head and the mattress. The width of your shoulders sets that gap, and the job of the pillow is to fill it so your neck stays level with the rest of your spine.

Get that measurement right and most pillow complaints disappear, but get it wrong and no amount of fluffing or folding will fix it.

Work Out The Gap You Need To Fill

Lie on your side on the mattress you actually sleep on, with no pillow at all. The distance between the outside of your shoulder and the side of your head is the height your pillow needs to hold once it’s compressed under the weight of your head.

For most adults that lands somewhere between 10cm and 15cm. But broader shoulders tend to need more and a softer mattress needs less, because your shoulder sinks into the surface and closes some of the gap on its own.

A second person is useful here. Ask them to look at you from behind and tell you whether your nose lines up with the centre of your chest. If your head tilts down towards the mattress, the pillow is too low. If it tilts up, it’s too high.

Firmness Is What Holds The Height

Height and firmness are easy to confuse because a pillow only keeps its height if it’s firm enough to resist your head. A soft pillow may measure 15cm on the shelf and compress to 8cm under load, which leaves a side sleeper’s neck bent all night. This is why side sleepers usually end up in medium-firm to firm territory, while front sleepers want something soft and flat.

Adjustable Pillows Remove The Guesswork

The difficulty with buying a pillow online is that you can’t test the height until it’s on your bed. Adjustable designs solve this by letting you change the fill after delivery.

Simba’s Hybrid™ Pillow is built around a core of foam Nanocubes® that you add or remove to set the height and firmness yourself. It’s a sensible pillow for side sleepers in particular, since the correct height is personal and rarely matches whatever a manufacturer picks as standard. Their AeroDown Pillow uses Simba Renew Bio™- a breathable down-alternative fiber – making it sit lower and softer to suit front sleepers or people who move between positions.

Temperature And Materials

Side sleepers have more head-to-pillow contact than back sleepers, so heat builds up faster.

• Foam cores hold warmth unless they’re perforated, channelled or made in an open structure.
• Down and down-alternative fills breathe well but compress, which affects height retention.
• Cool-touch covers help with contact temperature, and mesh side panels let air move through the pillow.
• Removable covers are worth having, since a pillow absorbs a surprising amount of moisture.

Support For The Rest Of Your Body

Side sleeping also rotates the hips, because the upper leg falls forward and pulls the pelvis with it. A pillow between the knees keeps the hips stacked and takes strain off the lower back, and a full-length design like the Simba Body Pillow does the same job while giving your upper arm somewhere to rest, which stops you from rolling forward onto your chest.

Testing A New Pillow Properly

A new pillow feels wrong for a few nights even when it’s right, because your neck has adapted to whatever you were using before. Give it a week before making a judgement.

What to watch for in that week:

• Neck discomfort that’s present on waking and eases within an hour points to height being wrong.
• Shoulder ache on the side you sleep on usually means the pillow is too low and your shoulder is taking the load.
• Waking with the pillow pushed out of position suggests it’s too firm for the gap you’re filling.
• Numbness in the arm you lie on is more often a mattress issue than a pillow one.

Replacing A Pillow On Time

Pillows are generally more affordable than mattresses, but people often keep them far longer than they should. The general guidance is that most standard pillows need replacing every one to two years, and the signs are easy to spot: if it no longer springs back into shape, or you wake with neck discomfort that eases during the day, it’s time for a replacement. An adjustable pillow like Simba’s buys you longer, since you can top up the fill as it settles, though the cover and core still wear eventually.

FAQs

How high should a pillow be for a side sleeper?

It should fill the gap between your shoulder and your head while you’re lying down, which for most adults means a loft of roughly 10cm to 15cm once compressed. Shoulder width and mattress firmness both shift that figure, so take the measurement yourself.

Should side sleepers use a firm or soft pillow?

Medium-firm to firm usually works best, because the pillow needs to resist the weight of your head without collapsing. A soft pillow that compresses flat leaves your neck bent towards the mattress for hours.

Can two pillows do the job of one tall one?

No – two pillows will slide apart during the night and create an uneven surface. A single pillow at the correct height is the best way  to give your neck the proper support it needs.

Do memory foam pillows suit side sleepers?

Yes, foam pillows can be good for side sleepers as they hold their height well and contour around the ear and jaw. 

Does the mattress affect which pillow I need?

Yes, and it’s a commonly missed factor. A softer mattress lets your shoulder drop into the surface, which reduces the gap the pillow has to fill. Changing your mattress often means your pillow height needs revisiting too.