Loft is the most important thing about a pillow and the spec almost nobody explains at the store. It simply means how tall the pillow holds your head. Get it right and your neck stays neutral all night. Get it wrong and no amount of cooling fabric or fancy foam will save your morning. Here is the height that actually works for each sleep position.
What loft really controls
Your spine has a natural curve, and your neck is happiest when it keeps that curve while you sleep, the same neutral line you hold standing with good posture. Loft is the tool that keeps your head level with your spine. Too much and your neck cranes up. Too little and it drops. Everything else is secondary.
Side sleepers: high loft, 4 to 6 inches
Lying on your side opens a wide gap between your head and the mattress because your shoulder is in the way. You need enough height to fill that gap and keep your head level. Broad shoulders or a firm mattress push you toward the top of that range or beyond. This is the position most likely to suffer from a too-thin pillow.
Back sleepers: medium loft, 3 to 4 inches
On your back the gap is smaller, so you need less height. The goal is to cradle the natural curve of your neck without pushing your head forward. Too tall here tucks your chin toward your chest and strains the back of your neck.
Stomach sleepers: low loft, under 3 inches
Stomach sleeping is tough on the neck because your head is turned to one side all night. If you sleep this way, you want the flattest pillow possible so your neck is not also craned upward. Many stomach sleepers do better easing toward their side over time.
The catch nobody mentions
These ranges are starting points, not guarantees. Your shoulder width, your mattress, and whether you move at night all shift the right number. That is the core problem with buying a fixed-height pillow: you are committing to one guess and hoping it lands. An adjustable-fill pillow lets you start in the right range and then fine-tune by adding or removing fill until your neck is truly level. Every Dreamy Blue pillow is built this way, so loft is something you set rather than something you gamble on.