How to Adjust Pillow Fill for Firmness and Loft

Can you add or remove fill in an adjustable pillow to change its firmness and loft?

Yes. Most adjustable pillows use a zippered opening that lets you remove or add fill to change loft height and firmness on demand. Pillow height is a primary, measurable driver of cervical spine alignment, and no single fixed loft fits every body, mattress, or sleep position equally well.

A fixed-loft pillow asks you to accept whatever height the manufacturer chose. It might suit your shoulder width and mattress firmness by luck, or it might leave your neck bent up or down every night with no way to change it. Sleep Foundation and the National Council on Aging both list adjustable-fill pillows, shredded fills, interchangeable inserts, and zippered gussets among their top picks, because sleepers can set the height that alignment rather than hoping a fixed height happens to fit.

Every Circadian pillow arrives full and adjusts through the same zippered opening, whether the material inside is buckwheat, wool, kapok, cotton, or shredded Dunlop latex. The steps below cover why loft matters, how to find your starting point, and how to remove or add fill until your neck stays level with your mattress.

Step 1: Why does adjusting your pillow's fill matter for neck and spine health?

Adjusting fill matters because pillow height directly changes cervical angle and pressure at the base of your skull. A 2016 biomechanics study found that raising pillow height increased cervical angle by 66.4 percent and lordosis distance by 25.1 percent, while a 2021 ergonomic review confirmed no single height works for every body.

The 2016 biomechanics study published in PMC measured cranio-cervical pressure and cervical spine alignment across four pillow heights. Going from the lowest setting to the highest reduced kyphosis distance by 43.4 percent as cervical angle and lordosis distance both increased. A separate 2021 ergonomic review concluded that pillow height is a primary determinant of spinal alignment and neck muscle activity, and that no universal optimal range exists because body dimensions vary so much from person to person.

Fixed-height pillows lock you into whatever loft the manufacturer chose. Adjustable fill turns loft into something you control instead. Circadian's zippered opening gives you direct access to the fill in every pillow in the lineup, so the same adjustment a lab makes to test four heights, adding or removing material, is what you do at home.

A stiff neck or numb arm that shows up regardless of sleep position usually means your loft is wrong in one consistent direction, not just an occasional bad night. If your pillow feels different every single night without you touching the fill, the fill has shifted or compressed unevenly and needs redistributing before you judge the height.

Before adjusting anything, you should be able to say whether your current pillow feels too high, too low, or roughly right. That one-word read becomes a specific starting-loft target once you check it against your mattress firmness and sleep position.

Step 2: How do you find your starting loft before adjusting?

Your starting loft depends on your mattress firmness and your sleep position together. Cleveland Clinic ties pillow height directly to mattress firmness, and side sleepers generally need more loft than back sleepers to keep the neck level with the spine.

A firmer mattress keeps your shoulder from sinking, which leaves a bigger gap between your head and the mattress for the pillow to fill, so it needs a thicker starting loft. A softer mattress lets the shoulder sink deeper, so a thinner pillow keeps the neck from bending upward. Sleep Foundation and NCOA add that side sleepers need more loft to bridge the gap over the shoulder, back sleepers need less to avoid pushing the chin toward the chest, and stomach sleepers need the least loft of the three.

Lie in your normal sleep position on your actual mattress, not a showroom floor, and notice where your neck bends. A chin tipping down toward the chest means the pillow is too high for that position. A head tilting back or a neck arching means it's too low. That's your reference point before you touch the zipper.

Guessing your ideal loft from a product description alone skips this step and usually leads to unnecessary back-and-forth. A pillow that felt right in a store often feels different on your own mattress at home, because mattress firmness changes how deep your shoulder sinks.

You should now have a specific direction, more loft or less loft, and a sleep position to test it in, ready to use whether you end up removing fill to lower the loft or adding fill back to raise it.

Photo: Rebekah Morgan Photography

Step 3: How do you remove fill to lower loft and soften firmness?

Unzip the pillow's side opening and remove fill in small handfuls, then lie down in your normal sleep position to retest. Work in small increments rather than removing a large amount at once. It's easy to take out more than you need and hard to judge the right amount by feel alone.

Every Circadian pillow arrives full, about 30 percent more than most sleepers keep, so there is room to take some out before the pillow reaches its intended feel. The Circadian Buckwheat Pillow makes this easiest to see because its fill is loose hulls, not batting, which makes incremental removal simple to control by the handful. Buckwheat pillow brands including Hullo and PineTales use the same zippered-access approach, since loose-hull fills are naturally suited to it.

Open the zipper fully, reach in, and pull out one handful of fill at a time. Lie down after each handful and check whether your neck stays roughly parallel to the mattress. Side sleepers can stop removing fill once the gap over the shoulder is filled without tipping the head down. Back sleepers can stop once the chin sits level, not tucked toward the chest.

Removing fill in large scoops instead of small handfuls is the most common mistake here, since it's much easier to take out too much than to judge by feel how much is still enough. If you overshoot, add fill back through the same opening rather than compressing what's left to compensate.

You should now have a pillow that feels noticeably lower and softer than when you started, with your neck staying level with the mattress in your usual position. Store any removed fill in a labeled jar or bag in case you want it back later.

Step 4: How do you add fill back to raise loft and firm the pillow up?

Add fill back through the same zippered opening whenever the pillow has compressed with age, or when a change in sleep position or mattress calls for more height. Every Circadian pillow arrives full, so most sleepers add material only after months or years of use, not right after purchase.

There is no separate pouch of extra fill included with a Circadian pillow. Fresh fill comes from a refill product, Buckwheat Hulls for Pillows for the Buckwheat Pillow, or the matching fill refill for wool, cotton, and latex pillows. The fill you removed in Step 3 gradually compresses over years of nightly use, and hulls or fibers that have flattened don't restore themselves on their own.

Open the zipper and add fill back in small handfuls, working in small increments so you don't overshoot. Retest after each handful in your normal sleep position. If you're sharing a bed with a partner who needs a different loft, add or remove fill before each of you settles in rather than trying to split the difference permanently.

Adding a large amount of fill at once risks overshooting into a loft that's too high, the same problem as removing too much at once. A pillow that feels lumpy after adding fill just needs redistributing by hand before you test it again, not a change in loft.

You should now have a pillow that matches the loft you identified in Step 2, whether that meant removing fill in Step 3 or adding it back here. A pillow that has compressed after years of use and reaches that same target loft again is a sign the refill worked.

Step 5: How do you know when the loft is right?

The loft is right when your neck stays roughly parallel to the mattress in your normal sleep position, with no gap under your ear on your side and no chin tucked toward your chest on your back. A 2025 individualized-height study found that a medium individualized height with neck support produced the cervical curve closest to natural standing alignment.

The right loft is the point where your body stops compensating for the pillow, not a fixed count of hulls or ounces of fill. NCOA and Sleep Foundation both frame this as keeping the head, neck, and spine in a straight line, regardless of fill type or brand.

After each adjustment round, sleep on it for two to three nights before deciding whether to change it again. A single night doesn't give you enough data, since normal aches from an old pillow can linger for a few days after switching. Our workshop's pillow expert, Lily, has tested every fill in the lineup for over ten years and sleeps on the Buckwool Hybrid herself. The buckwheat side gives her the firm alignment her neck needs, and she switches to the wool side on nights when she wants something gentler.

If you keep adjusting the same pillow every few days without settling on a feel, the loft probably isn't the actual problem. Check your sleep position and mattress firmness again using Step 2 before assuming the fill needs more work.

You should be sleeping through the night without waking specifically because of neck position, and a friend or partner checking your side-sleeping profile should see a straight line from ear to shoulder. That straight line is the same alignment target every source in this guide points to.

What are the most common mistakes when adjusting pillow fill?

The most common mistakes are removing or adding fill in large amounts instead of small handfuls, judging loft after a single night instead of two to three, and guessing at starting loft instead of checking it against mattress firmness and sleep position first.

• Overcorrecting in one pass. Removing a large scoop of fill instead of a handful makes it hard to know whether the new loft is right or just different. Fix: work in small increments and retest between each one.
• Judging loft after one night. Lingering stiffness from your old pillow can make a correctly adjusted pillow feel wrong for the first night or two. Fix: give each adjustment two to three nights before changing it again.
• Skipping the starting-loft check. Adjusting fill without first checking mattress firmness and sleep position against Step 2's guidance means you're guessing at a target instead of working toward one. Fix: reread Step 2 before touching the zipper.
• Mixing fill from different products. Adding wool fill to a buckwheat pillow, or the reverse, changes the feel and firmness in ways that aren't predictable. Fix: use the matching Circadian fill refill, buckwheat hulls, wool, cotton, or latex, for whichever pillow you're adjusting.

When does this loft-adjustment approach need to change?

This approach changes when your mattress firmness changes, when your sleep position shifts long-term, such as after surgery or during pregnancy, or when a fill has compressed enough that adding fill back no longer restores the loft you want, which signals it's time for a refill rather than a small addition.

A new mattress is the most common trigger. Firmer mattresses need more loft to fill the gap over your shoulder, softer mattresses need less, so a mattress swap means starting back at Step 2 rather than assuming your old loft still applies. Buckwheat hulls that have flattened past what fresh fill can fix are a sign to order a hull refill, such as Buckwheat Hulls for Pillows, rather than continuing to add flattened material back.

Sharing a bed with a new partner, recovering from a neck or shoulder injury, or switching your primary sleep position for an extended period are the other common triggers. Each one calls for restarting the process at Step 2 with the new baseline, not just tweaking fill from where you left off.

What do real adjustment scenarios look like?

Three common scenarios cover most adjustment situations: a side sleeper switching to a firmer mattress, a back sleeper whose pillow has compressed after years of use, and a combination sleeper sharing a bed with a partner who needs a different loft.

Scenario 1: The side sleeper with a new firmer mattress. A side sleeper who just replaced a soft mattress with a firmer one notices her shoulder no longer sinks as deep, which leaves a bigger gap for the pillow to fill. She adds two handfuls of fill back into her Circadian Organic Wool Pillow through the zipper, testing after each handful until her neck stays level with the new, firmer surface.

Scenario 2: The back sleeper with a compressed pillow. A back sleeper who has used the same buckwheat pillow for six years notices it feels flatter than it used to, and his neck tips back slightly at night. The hulls have gradually lost their interlocking shape from years of nightly compression. He orders a hull refill and adds fresh hulls through the zipper rather than replacing the whole pillow.

Scenario 3: The combination sleeper sharing a bed. A combination sleeper who shares a bed with a partner who prefers a much lower loft keeps her Circadian Buckwheat Pillow on the firmer, higher side while her partner removes several handfuls from his own pillow. Because the adjustment happens per pillow rather than per bed, each person reaches their own target loft without compromising the other's.

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