When you crawl under the covers, do you want to sink into a soft mattress that conforms to every curve of your body? Or do you think it’s more comfortable when you feel like you’re lifted and supported “on top” of your bed? What we’re describing here is firmness, and it’s one of the main factors you’ll consider when choosing a new mattress.

Typically, mattress companies will provide a firmness score that falls between 1 (softest) and 10 (firmest). There’s no universal right or wrong firmness level; the ideal feel for you will depend on things like your sleeping position, whether or not you’re prone to back or joint pain, and plain old personal preference—and we’ll get into all of that below.

In this mattress firmness guide, sleep researchers and spine experts offer their insights to help you land on the best bed to fit your needs (a.k.a. you’ll be one step closer to achieving a full REM cycle).

In this article

• Mattress firmness levels
• Firmness and sleeping positions
• Firmness versus support
• Tips for choosing a mattress firmness
• FAQs

While mattress firmness is scored on a scale of 1 to 10, it’s not a totally standardized score. That’s because the same bed probably won’t feel identical to two different people due to factors like body size. “A petite person or a child may find a mattress firm when a larger person does not,” Kevin Lees, DC, a chiropractor based in Arizona, tells SELF.

This also helps explain why there’s no single “correct” firmness that applies to all people. With that in mind, having a grasp of what it means for a mattress to be classified as soft, medium-firm, or firm (the most common levels you’ll see when perusing product descriptions—and our recs) can help you pinpoint what will work best for you.

Just because a mattress is soft doesn’t mean you’ll hit the floor, as if you were hopping on a partially deflated air mattress. Rather, “a softer mattress should still feel supportive but may compress easier under higher-pressure areas,” says Dr. Lees. “It may feel more contouring or adaptive [than a firmer option], and sometimes, it may feel as if the person is sinking in.”

A softer mattress level often suits side sleepers “because [this firmness level can] relieve pressure on the shoulders and hips,” Shelby Harris, PsyD, a board-certified behavioral sleep medicine expert and director of sleep health at Sleepopolis, tells SELF. But because softer beds don’t hold up the spine as well, stomach and back sleepers can find them uncomfortable.

Dr. Lees adds that soft mattresses tend to be great options for kids. “A softer surface may be more adaptable to their body shape and still provide the support they need,” he says.

One of our favorite soft mattresses:

• Puffy Lux Hybrid (featured in Best Mattresses for Couples)

Neither too soft nor too firm, medium-firm mattresses would make Goldilocks happy. Research supports that they’re generally the best for easing back pain and promoting good sleep quality too. On these, you can expect a bit of the “sinking” feeling you get on a soft mattress but with more lift.

Medium-firm mattresses can support your spine and provide some cushion, Dylan Petkus, MD, a sleep medicine specialist, tells SELF, adding that this makes them a good pick for back sleepers and combination sleepers (who cycle through different positions while sleeping). If you’re not sure where to start, medium-firmness is a safe bet, given its versatility.

Some of our favorite medium-firm mattresses:

• Helix Midnight (featured in Bed-in-a-Box Mattresses)
• Nolah Evolution (featured in Best Mattresses for Sex)
• Saatva Classic (featured in Best Mattresses for Back Pain)

If you sleep on your back or stomach, a firm mattress could work best for you because it “provides the extra support needed to keep the spine as neutral as possible,” Dr. Lees says. For back sleepers, a mattress that is too soft can add stress to the natural curve in your lower back, and for stomach sleepers, it can exacerbate an overextension and rotation of the neck, he adds. People with larger bodies tend to find firmer mattresses optimally supportive.

For some, however, a firm mattress can lead to joint pain and tossing and turning, according to Dr. Lees. “Depending on the size of the person [lying on it], a firm mattress may create gaps in support along the body, which can also increase stress on the spine, pelvis, and hips,” he adds.

Some of our favorite firm mattresses:

• Emma Hybrid Comfort (featured in Best Mattresses)
• Plank Firm (featured in Best Memory Foam Mattresses)
• Saatva Latex Hybrid (featured in Best Latex Mattresses)

In addition to body size and simply what feels the best, sleeping position is a top indicator of what level of firmness is best for you. Below, experts play mattress matchmaker, connecting each sleeping position with its ideal firmness level.

If you sleep on your side, a soft or medium-firm mattress is a good option for you, according to Dr. Harris. In this position, you’ll put more pressure on your shoulders and hips, so you want to be able to sink in enough to cushion those areas while still accessing enough support to hold up your lumbar region and keep your spine in alignment.

If you're a strict stomach sleeper, having a sturdy sleeping surface is important for encouraging healthy spinal curvature. “Stomach sleepers need a firm mattress to prevent sinking and protect their lower back,” Dr. Petkus says. “The extra support keeps the body from sinking in, maintaining proper spine alignment.”

Back sleepers typically benefit from a mattress that isn’t too soft or too firm, Dr. Petkus says. When you sleep on your back on a firm mattress, that natural curve in your lumbar spine is left floating off the bed, with nothing to support it. But if your bed is too soft, your back can collapse down into the bed (picture the rounded, contracted back position you assume in cat pose in yoga). “Back sleepers do best with a medium-firm mattress to support the natural curve of the spine,” he says.

Combination sleepers move around a lot around at night, shifting from their back to their stomach to their side. For these folks, a medium-firm mattress is a good place to start because it provides a balance of comfort and support, which Dr. Petkus says should accommodate various positions.

Firmness and support are often used interchangeably, but they’re actually not synonymous. Firmness measures (subjectively!) how a bed feels to you when you lie on it. Support, on the other hand, refers to how well a bed holds up your body and spine in neutral alignment while you’re sleeping.

“Firmness is the feeling of the mattress, how much cushion or give it allows,” Dr. Lees says. “Support is the pressure the mattress gives back, ensuring that heavier areas don’t sink too far into the bed, leaving a person sleeping in a C shape or an otherwise awkward position that could make them feel very sore.”

Put simply, the best way to make sure a mattress’s firmness is right for you is to give it a whirl, Dr. Lees says. “Since each person is a different size and shape and has different sleeping preferences, you should always test the mattress personally,” he says. If you’re ordering your bed online, take note of trial periods, warranties, and sneaky hidden costs like return fees. Also, take stock of reviews from customers who have already tried the bed in question. (And, ahem, check with us too; Our experienced testers use our mattress-testing methodology to personally evaluate beds we recommend.)

Before shopping, Dr. Petkus suggests considering what you like (and don’t) about your current bed, and using that as a personal mattress firmness guide for yourself and any bedmates you have.

If a mattress feels comfortable to you when you lie down on it, Dr. Harris says that’s a good sign that it’s the right mattress firmness for you. However, body weight and sleeping position are also contributing factors to what feels dreamy. Heavier individuals and stomach sleepers may prefer a firmer mattress for extra support; combination and back sleepers typically do well with a medium-firm mattress; and a softer mattress can be a good choice for side sleepers and smaller people.

The mattress firmness considered “healthiest” for you will depend on a handful of factors like your body size, sleeping position (side, stomach, back, combination), and personal preference. Whatever feels most comfortable to you and supports neutral spinal alignment will be the best bet for your sleep quality.

If you’re having a hard time getting comfortable in one position or you toss and turn a lot at night, that could be a sign that your mattress is too firm or too soft, according to Dr. Lees. “Waking up very stiff or sore is also a good indicator,” he adds. ”Mattresses don’t last forever, so if your mattress initially gave you a great night’s rest but now you feel tired and [achy] in the morning, it may be time for a new mattress.”

Related:

• The Best Mattresses on Amazon
• The Best Hybrid Mattresses
• The Best Affordable Mattresses