Pillows are sold on softness, firmness and material. The property that determines whether one works is height, and it is decided by your body rather than your preference.

What a Pillow Is For

Filling the gap between your head and the mattress so the neck continues the line of the spine.

Too high pushes the head up and holds the neck bent for hours. Too low lets it drop. Either sustained through a night produces the stiffness people wake with.

Nothing about the material changes this. A superb pillow at the wrong height is the wrong pillow.

The Gap Depends on Position

• Side sleeping: the widest gap, from mattress to the outside of the shoulder
• Back sleeping: moderate, supporting the neck’s natural curve
• Front sleeping: very small, so almost no pillow at all
• Broad shoulders: more height than average in the same position
• A soft mattress: less, because the shoulder sinks into it

Pillows with removable layers, of the kind at nuzzle-pillows.com, exist because that gap is personal and a fixed loft cannot match everybody’s.

The Test

Lie in your usual position, on the mattress you actually sleep on, and have somebody look from the front.

The head should be level, with the neck continuing the straight line of the spine rather than angled up or dropping toward the shoulder.

Ten seconds of that settles the question more reliably than any product description.

The Mattress Is Part of the Equation

Frequently forgotten. A firm mattress lets the shoulder sit proud, which widens the gap. A soft one lets the shoulder sink, which narrows it.

The same person needs a different pillow height on a different bed, which is why hotel pillows so rarely suit.

Two Pillows Is Not the Answer

Stacking to gain height angles the head forward rather than supporting it level, and the two shift relative to each other during the night.

One pillow at the correct height works considerably better.

Give It Several Nights

A new height feels wrong at first even when it is correct, because your neck has adapted to whatever it was doing before.

Three or four nights is a fair test. Judging after one produces a cycle of buying pillows.

Firmness Is Not Height

A soft high-loft pillow flattens under a head and becomes a low pillow.

What matters is the height it holds once you are lying on it, not the height on a shelf.

If Nothing Works

Persistent neck pain is worth raising with a GP or physiotherapist rather than solving by purchase.