Why Pillow Height Is a Per-Body Parameter, Not a Fixed Spec

The problem with standardized height

Most pillow manufacturers ship a fixed height: 5 inches for side sleepers, 3 for back sleepers, or whatever the factory decided would fit the median buyer. That approach ignores a measurement problem every chiropractor treating neck pain already knows: the distance between your ear and the mattress changes with shoulder width, mattress firmness, and body weight, so a single fixed number cannot work for everyone.

A 2023 clinical study of 84 people found that personalized pillow-height adjustment produced clinically meaningful neck pain reduction in about half of participants. That result supports treating height as something you measure and re-check rather than something a brand sets once at the factory.

This post walks through why height matters, what changes the number you need, and how to approach it as a parameter you adjust rather than a spec you buy.

What the measurement actually tracks

Pillow height is supposed to fill the gap between your neck's natural curve and the mattress surface, keeping your cervical spine in the same neutral line it holds when you stand upright: ears stacked over shoulders, chin level, no forward tilt or backward drop.

That gap changes based on three inputs:

• Shoulder width. A wider shoulder creates a taller gap when you sleep on your side.
• Mattress firmness. A softer mattress lets the shoulder sink deeper, which shrinks the gap.
• Body weight. Heavier sleepers compress a mattress more, which also shrinks the gap.

Because all three inputs vary per person, the correct height is a function of your specific body and mattress, not a universal number.

Side sleepers versus back sleepers

Side sleeping opens a wider gap between the ear and the shoulder than back sleeping does, so peer-reviewed biomechanical research on side sleepers points to individualized height over a single chart number. A side sleeper's shoulder width determines how much height is needed to keep the spine level.

Back sleepers need less height because the gap between the back of the head and the mattress is smaller, but the same principle applies: the right height depends on neck length and how far the head sinks into the mattress.

Stomach sleepers break the pattern entirely. Real height under the neck forces the head up and twists the cervical spine sideways for hours, so the correct height for a stomach sleeper is often close to none.

What changes the number over time

A pillow that worked for months can stop working when one of the three inputs shifts:

Mattress softening. A mattress that compresses more over its first year changes how far the shoulder sinks, which changes the height the neck needs. If the mattress gets softer, the same pillow height becomes too tall.

Weight change. Gaining or losing 10–15 pounds shifts shoulder width just enough to matter for side sleepers. Weight gain usually increases shoulder width, which increases the required height.

Mattress replacement. Switching from a soft mattress to a firm one changes how far the shoulder sinks, so the same pillow height that worked before is now too tall because the shoulder no longer compresses the surface as much.

A 2023 study found that periodic height re-adjustment mattered more than the initial setup, which is why adjustable designs with a side zipper exist: they let you reset height when the inputs change instead of buying a new pillow.

How adjustability solves the fixed-spec problem

Fixed-height pillows from brands like Tempur or Purple ship at one height, so a sleeper either fits the mold or does not. If your shoulder width or mattress firmness does not match the factory preset, the pillow cannot correct for it.

Adjustable pillows ship with extra fill—about a third more than most people keep—so height gets set through a side zipper on night one. When the mattress or body changes, height gets reset the same way: open the zipper, add or remove material, close it again.

That approach treats height as a tunable parameter rather than a fixed spec, which matches how chiropractors approach the problem: firmness and adjustability matter more than any one material or brand name.

Firmness interacts with height

A pillow can be the right height and still fail if the firmness is wrong. A fill that compresses too easily under the head's weight collapses the gap even at the correct starting height, so the neck sags overnight.

A 2025 systematic review found no single pillow type shows clear superiority for neck pain, disability, or sleep quality, which is why chiropractors generally weigh firmness and adjustability together. A firm fill that holds a contoured shape—like interlocking buckwheat hulls or slow-pour Dunlop latex—keeps the neck supported after the initial setup.

Softer fills like kapok or cotton compress more easily, which works well for stomach sleepers who need very little height but can cause side sleepers to lose support partway through the night.

Real-world re-adjustment example

Profile: side sleeper with a desk job, waking with a numb shoulder and stiff neck after 8 months on the same pillow. A mirror check showed the ear sitting well below the shoulder line, meaning the pillow had compressed below the height the shoulder gap needed. Adding fill through the side zipper brought the ear back in line with the shoulder, and the shoulder numbness resolved within 10 days.

Profile: someone who replaced a soft mattress with a firmer one 3 months ago and started getting mid-morning neck stiffness. The firmer mattress changed how far the shoulder sank, so the same pillow height that worked before was now too tall. Removing a small amount of fill through the zipper brought the neck back to neutral within a few nights.

The method, not the brand

Chasing a single "best chiropractor pillow" misses that the right answer depends on your shoulder width, your mattress, and how those inputs change over time. The method that works is measuring the gap, setting height to match, and re-checking when something changes.

Every number in this post comes from peer-reviewed research on cervical biomechanics or clinical trials on personalized pillow adjustment. The consistent finding is that fit matters more than brand, and adjustability matters more than any one fixed spec.

Originally published on Circadian.