--- title: "How thick should a knee pillow be? · The Side Sleeper" url: https://thesidesleeper.com/knee-pillows/thickness/ published: 2026-10-05 updated: 2026-10-09 --- [Knee pillow guides](https://thesidesleeper.com/knee-pillows/) # How thick should a knee pillow be? **Nell, the Side Sleeper** Updated October 9, 2026 · Data collected October 5, 2026 · [How we research](https://thesidesleeper.com/how-we-research/) **Thick enough to hold your top knee level with your top hip, and no thicker.** For most people that lands somewhere in the range most knee pillows are sold in: **5 to 7.2 inches** for the compact between-the-knees shapes, and 3 to 6.5 inches for the long ones that run down the thigh or the whole leg. Your own number depends on your hips and thighs, so a five-minute towel test (below) beats any chart. ![Folded bath towels stacked in neat piles.](https://thesidesleeper.com/_astro/folded-towels.gUXhh7ca_11Af3k.jpg) Ordinary bath towels are all you need to find your number. Photo: [rawpixel](https://www.rawpixel.com/image/5907616/bath-towels-free-public-domain-cc0-photo) When you sleep on your side, your top leg wants to slide forward and down until the knee rests on the mattress or on your other knee. That rolls your pelvis forward and twists your lower back. It's also why the outer edge of your top hip can ache by morning. A knee pillow's whole job is to stop that slide by filling the gap between your knees. Too thin, and the top knee still drops. Too thick, and the pillow pushes the top leg _up_, which tilts things the other way. The right thickness is the one that leaves your top thigh running roughly parallel to the mattress. ## Find your number: the level-knee towel test You need two or three bath towels, a tape measure, and either a helper or a phone propped up at the foot of the bed. 1. **Lie the way you really sleep.** On your usual side, on your own mattress, with your usual head pillow, knees bent the way they normally are. 2. **Start with one folded towel between your knees.** Fold it to roughly the footprint of a knee pillow, about the size of a paperback. 3. **Check the line from hip to knee.** Seen from the foot of the bed, your top thigh should run about parallel to the mattress: the top knee neither sagging below the hip nor propped above it. 4. **Add or remove a towel and check again.** Stop when the thigh looks level and your top hip feels like it can let go. 5. **Measure the stack.** Slide the towels out without unfolding them and measure their height. That's the gap your knees want. Towels and memory foam squash differently, so treat your measurement as a guide to within an inch rather than an exact spec. If you land between two sizes, the next section explains why going slightly thicker is usually the safer bet. ## Why the number on the listing isn't the gap you get Two things make a pillow hold your knees closer together than its listed thickness suggests: - **The listed height is the outside measurement.** Hourglass and heart shapes have a curved channel on each side for your knee to sink into, so the gap at your knees is less than the height at the pillow's thickest point. - **Foam settles under your leg.** Memory foam softens with body heat and gives under weight. That's the point of it, but it means the gap at 3 a.m. is smaller than the gap on the box. So if your towel test says 5 inches, a pillow listed at 5 inches is likely to sit a little under that in use. ## What's actually on sale I went through the listings and manufacturer pages of 25 of the best-selling knee and leg pillows to pull out one number: how thick each one is. 14 of the 24 knee pillows state it clearly: - MINUPWELL Knee Pillow (knee-to-ankle): 3″ - ROKAFU Knee Pillow 11" (thigh + knee): 3″ - Xtra-Comfort (Vive Health) Full Knee Pillow 29": 4″ - TULARIS Heart Knee Pillow with Adjustable Strap: 5″ - ComfyInLove Knee Pillow with Cooling Gel: 5.5″ - Cushion Lab Side Sleeper Knee Pillow: 5.5″ - BlissTrends Memory Foam Knee & Leg Pillow (Large): 5.7″ - 5 STARS UNITED Knee Pillow for Side Sleepers: 6″ - Vertdens Leg Pillow: 6″ - HOMBYS Shredded Memory Foam Knee Pillow 6.5": 6.5″ - DailyCuddles Memory Foam Knee Pillow with Strap: 6.9″ - TranquilMoments Heart-Shape Knee Pillow, Cooling Cover: 7.2″ - ComfyInLove Heart-Shaped Knee Pillow: 7.2″ - Coop Home Goods Adjustable Knee Pillow: 5–8″ adjustable Listed thickness (outer height) of the 14 knee pillows that state it clearly. Median 5.85″. Snapshot October 5, 2026. [See every pillow and its full specs](https://thesidesleeper.com/knee-pillows/compared/). Three things stood out: - **10 of 24 don't give a usable thickness.** That includes the #1 best seller, the Contour Legacy Leg & Knee Pillow, with 43,734 reviews. Its listing gives length and width but leaves the height to the photos. Others list three numbers without saying which one is the gap between your knees. - **Long pillows are thinner.** Pillows that support the whole thigh or leg (3–6.5″) spread your leg's weight along their length, so they don't need the height of a compact knee pillow. - **Only one is adjustable.** The Coop Home Goods Adjustable Knee Pillow comes with removable foam inserts. By my arithmetic from its stated 8″ height and 1″ and 2″ inserts, that's 5″ to 8″ in 1″ steps. ## What about the "4 to 6 inches" rule? Many sleep guides give one answer: a knee pillow should be 4 to 6 inches thick, thicker if you're heavier. Checked against what's actually on sale, it leaves out a lot of the market. Of the 14 knee pillows that state a thickness, **7 fall inside 4–6″**, 5 are thicker and 2 are thinner. The thicker ones include the ComfyInLove Heart-Shaped Knee Pillow at 7.2″, sold as a standard knee pillow, not a special size. Body weight is a rough stand-in for the real measurement. The gap your knees need is how far your top knee has to be lifted to sit level with your top hip, and that depends on how wide your hips are compared with your knees and how much thigh sits between them. Two people of the same weight can need different pillows. Treat 4 to 6 inches as a starting point, and let the towel test above give you your own number. ## Matching a pillow to your number ### Under about 4 inches Look at the long, flatter styles (Long (thigh + knee), Full-leg) or a soft fibre-filled pillow you can squash down. ### About 5 to 7 inches That's the standard compact knee pillow. Pick by listed height, then lean slightly thicker to allow for the channel and the foam settling. ### Over 7 inches, or you're not sure Consider the adjustable-insert pillow. A pillow you can tune beats guessing. ## When it isn't the pillow If your hip hurts at night whatever you put between your knees, or the pain wakes you most nights, see a doctor or physiotherapist. Persistent pain on the outer hip when lying on your side is common, especially from your 40s onward, and it has causes a pillow can't fix. If it's the pillow that seems to be making it worse, [here's how to tell why](https://thesidesleeper.com/knee-pillows/hurts-hips/). The NHS has a plain-English overview of one of the most common, [greater trochanteric pain syndrome](https://www.nhsinform.scot/illnesses-and-conditions/muscle-bone-and-joints/leg-and-foot-problems-and-conditions/greater-trochanteric-pain-syndrome/). ## Quick answers ### Is a 4-inch knee pillow thick enough? It is if your own knee gap is about 4 inches. That's on the thin side for a compact knee pillow: the best sellers that state a thickness run 5 to 7.2 inches. Four inches suits narrow hips, or a long pillow that runs down the thigh, where 3 to 6.5 inches is normal. ### Is a thicker knee pillow better? No. A pillow taller than your knee gap pushes your top knee above your hip and holds the leg open all night, which can leave the outer hip, groin or lower back aching. The right thickness leaves your top thigh running level with the mattress. ### How do I measure the knee gap I need? Lie on your usual side with your knees bent, and stack folded bath towels between your knees until your top thigh runs parallel to the mattress. Slide the stack out without unfolding it and measure its height. Foam settles under your leg, so if you land between two sizes, lean slightly thicker. ### Should a knee pillow be firm or soft? Firm enough to hold its height all night, which is why 19 of the 24 best sellers are solid memory foam. Shredded foam and fibre are softer and squash further. That helps if a pillow feels too tall, but leaves less height by morning. ## Sources - Pillow dimensions: Amazon US listing text and manufacturer product pages, collected October 5, 2026. Full list with the status of every number: [knee pillows compared](https://thesidesleeper.com/knee-pillows/compared/). - Side-lying hip pain background: [Greater Trochanteric Pain Syndrome, StatPearls (NCBI)](https://www.ncbi.nlm.nih.gov/books/NBK557433/). ## Keep reading [### Why sleep with a pillow between your knees?](https://thesidesleeper.com/knee-pillows/benefits/)[### Pillow between your knees hurts your hips?](https://thesidesleeper.com/knee-pillows/hurts-hips/)[### How to use a knee pillow](https://thesidesleeper.com/knee-pillows/how-to-use/)[### Knee pillow vs body pillow vs a regular pillow](https://thesidesleeper.com/knee-pillows/vs-body-pillow/)[### Knee pillow shapes, explained](https://thesidesleeper.com/knee-pillows/shapes/)[### Knee pillow fillings, explained](https://thesidesleeper.com/knee-pillows/fillings/)[### Knee pillow listings, by the numbers](https://thesidesleeper.com/knee-pillows/findings/)[### Knee pillows compared](https://thesidesleeper.com/knee-pillows/compared/)