How to Adjust Pillow Fill for Firmness and Loft

Updated: September 2, 2026

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

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

A fixed-height 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. Shredded-fill pillow brands such as Coop, Naturepedic, and Brooklinen also rely on a zippered opening to let owners add or remove material.

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 height matters, how to find your starting point, and how to remove or add fill until your head sits right for the way you sleep.

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 height the manufacturer chose. Adjustable fill turns height 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 height 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-height target once you check it against your mattress firmness and sleep position.

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

Your starting height 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 height 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 height. 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 height 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 height 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 height 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 height or less height, and a sleep position to test it in, ready to use whether you end up removing fill to lower the height or adding fill back to raise it.

Photo: Rebekah Morgan Photography

Step 3: How do you remove fill to lower height 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. Wool is the exception. It comes in flat layers, not loose fill, so you work from the outside instead of pulling at it. Slide your fingers under the topmost layer nearest the opening and draw it out slowly, whole. Often the wool lies in soft layers, some joined at a fold, so what you see through the zipper is a folded edge and there is no separate sheet to find. Follow it to the nearest fold and open it there. The folds are where wool parts cleanly and where it lies flat again. Keep every layer whole, never reach into the middle, and keep what comes out flat and dry: it goes back in any night you want the height back. How it feels in the first minute can fool you, so check where your head sits as well as how it feels. On your side, your head should rest level with the rest of your body, tipped neither toward the ceiling nor toward the mattress. On your back, the pillow fills the hollow under your neck and stays lower under your head, so you rest looking straight up. If you overshoot, put some back the same night. Nothing you take out is lost.

Every Circadian pillow arrives full, with about 30% more fill than most people keep, so you can shape it to your own neck. 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 where your head sits. Side sleepers can stop removing fill once the gap over the shoulder is filled without tipping the head down. Back sleepers can stop once they rest looking straight up, chin neither tucked toward the chest nor tipped back.

The most common mistake here is stopping too early. The feel in the first minute can mislead you, so check where your head sits, not only how it feels. 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 head level with your body on your side, or looking straight up on your back. Store any removed fill in a labeled jar or bag in case you want it back later.

Can you change the height, and can you get more material?

Two different questions, and most brands answer only the first. A pillow that opens with nothing to put back in it goes flat on the same schedule as one that never opened.

Adjustability runs in both directions, and taking material out is the half most people use. Ours arrive full, with about 30% more than most owners keep, so you can shape the pillow to your own neck. Most owners start by taking some out and setting the height to their own shoulder. Refill bags exist for the other direction, years later, when the material has settled.

The evidence for adjustability got better in 2026. A randomised crossover trial put an adjustable-height pillow against four fixed ones, with 30 adults. It measured comfort, cervical muscle oxygen and recovery. The adjustable one came first on all three. Its authors put it this way: “DA pillows may enhance cervical oxygenation, adaptive neuromuscular control, and comfort compared with fixed-height systems.”

Two honest limits on that trial. The adjustable pillow it used was air-based rather than a fill you take out by hand, and the sample was 30 young adults. So it supports adjustability as a principle rather than testing any particular pillow, ours included. Worth noting too that its fixed latex insert scored lowest of the inserts, and a shredded latex pillow that opens at a zipper is the opposite construction.

Against that, here is what the market offers. 20 of 20 buckwheat brands say the pillow can be opened. 12 say they sell a refill, 1 say they do not, and 7 publish wording that answers it neither way.

How we checked. A desk study. Every cell is the brand's own published wording, read on its own product page between February and May 2026, with no figure inferred and nothing taken from a review site or a marketplace listing. Where a brand publishes no figure the cell reads not published, and that counts as a finding, because a buyer reading that page cannot know it either. Our own row is graded by the same rule as every other. Prices and policies move, so the price columns are the capture-window figures and not a live quote. The disclosure counts are what this study is about and they move far more slowly.

Sources for this section

• Dynamic versus fixed pillow height systems and cervical muscle function: a randomized crossover trial, Kiatkulanusorn S, Luangpon N, Klarod K, et al., European Journal of Physical and Rehabilitation Medicine, 2026.
• Ergonomic consideration in pillow height determinants and evaluation, Healthcare (Basel), 2021.

Step 4: How do you add fill back to raise height 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. With wool, lay one whole layer back in flat against the others instead, and add a second only if the first is not enough. Retest after each handful in your normal sleep position. If you're sharing a bed with a partner who needs a different height, 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 height that's too high, and too high is the one that hurts, because it holds the chin toward the chest. A pillow that feels lumpy after adding fill just needs redistributing by hand before you test it again, not a change in height.

You should now have a pillow that matches the height 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 height again is a sign the refill worked.

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

The height is right when your head rests level with your body on your side, with no gap under your ear. On your back, the hollow under your neck is filled and you rest looking straight up, chin neither tucked nor tipped 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 height 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 tie the right height to your sleep position, whatever the 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. The Buckwool Hybrid Pillow is built for exactly this kind of night-to-night range: the buckwheat side gives the firm alignment a stiff neck needs, and the wool side offers something gentler when less pressure feels better.

If you keep adjusting the same pillow every few days without settling on a feel, the height 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 on you should see your head level with your body on your side. On your back, they should see your face pointing straight up.

What are the most common mistakes when adjusting pillow fill?

The most common mistake is stopping before the height is really right. The feel can fool you, so keep checking where your head sits until it rests level on your side or looks straight up on your back. Do not make the other three either: pulling wool out in bits when it should be lifted out one whole layer at a time, opened at a fold, judging height after a single night instead of two to three, and guessing at starting height 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 height is right or just different. Fix: work in small increments and retest between each one.
• Judging height 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-height 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 height-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 height 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 height 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 height 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 height.

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 lays one whole layer of wool back into her Circadian Organic Wool Pillow through the zipper, flat against the others, then lies down again, and adds a second layer only because her neck still drops.

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 height 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 height without compromising the other's.

Frequently Asked Questions