How to Choose a Mattress for Kids & Teens: Firmness, Size, & More

Most mattress advice is written for adults and the aches we collect over the years. Back pain, stiff hips, a shoulder that's been barking since that one ski season. It makes sense, since grown-ups are usually the ones doing the shopping. But a kid or a teenager is different since they’re typically not trying to fix an old injury. They're growing, they're hard on a bed, and they'll sleep on whatever you pick for the better part of a decade.

We see a lot of families come through the showroom, and the questions parents ask are nothing like the ones we field from adults shopping for themselves. So here's a guide built around what matters when the sleeper is five, twelve, or fifteen, rather than forty-five.

Buying for a Kid vs. Adults

A growing body has different priorities than a settled one. A child's spine is still developing, so support comes first, ahead of plushness. The bed needs to survive years of jumping, spills, and growth spurts. And kids spend more hours asleep than they ever will as adults, which means what the mattress is made of matters more, not less.

Firmness Goes by Age

Surprisingly, the younger and lighter the kid, the firmer the bed should be. A small body doesn't weigh enough to press into a soft comfort layer, so a plush mattress just leaves them lying on top of it with their spine unsupported. As they get bigger, they can use a little more give.

A rough guide:

• Toddlers moving out of a crib (about ages 2 to 5): firm to medium-firm, roughly 7 to 8 out of 10.
• School-age kids (6 to 12): medium-firm, around 6 to 7.
• Teens: medium to medium-firm, with lighter teens and side sleepers wanting it a touch softer, and bigger or stomach-sleeping teens wanting it firmer.

The mistake we see most is chasing softness too early because it seems cozier. For a young child, support matters more than cushion, and a bed that's too soft lets their hips sink and pulls their spine out of line.

What Size Mattress to Buy

Kids will do fine on a twin, but teens usually don't. A standard twin is only 38 inches wide, which gets cramped fast once a growth spurt hits, especially if they like to read or do homework sprawled across the bed.

• Twin XL adds 5 inches of length, good for a tall teen in a smaller room.
• Full gives them real room to stretch out, and it's a smart pick for a kid around 10 to 12 who's about to hit puberty. They grow into it instead of out of it.
• Queen, if the room and budget allow, can carry them into early adulthood without another upgrade.

If your kid is on the taller side or still climbing, it's worth sizing up before they need it, and it's one of the easiest ways to get more years out of a mattress.

Materials and Safety (What to Check on the Label)

Kids are more sensitive to what's in a mattress than adults are. They take in more relative to their size, and their lungs and immune systems are still developing, so it's worth knowing what's in their room. 

Below are key certifications that confirm if a bed has been independently tested and therefore safer than those that haven't been:

• CertiPUR-US for the foams, which means no harmful flame retardants or heavy metals and low VOCs.
• GREENGUARD Gold for low chemical emissions. This is the one aimed at sensitive groups, such as children.
• OEKO-TEX or GOTS if you want certified or organic textiles.

Look for fiberglass-free construction, too. A little new-bed smell is normal and will fade, but ventilation speeds it along, so give any new mattress a day or two to air out before sleeping on it. 

A few of the mattresses we carry at Sleep Basil with these certifications include our Natural Latex Mattress Collection, Helix Mattresses, and more. 

Durability and Value

It's tempting to grab the least expensive mattress for a kid, on the logic that they'll outgrow it anyway. The catch is that the budget foam beds in the $200 to $500 range will develop permanent dents within a couple of years of daily use, and a sagging bed is a bad bed for a growing spine.

Do the math on cost per year instead of sticker price. A better-built mattress a kid sleeps on for eight to ten years works out to about the same yearly cost as replacing a cheap one every two or three years, except they sleep well the whole time. Coils and hybrids, in particular, hold up better to the beating kids give a bed than thin all-foam does.

The Teen Years Add a Few Wrinkles

Teenagers come with their own needs. They tend to run hot, especially through puberty, so a bed that breathes (a hybrid, or a cool cover) keeps them from waking up sweaty. If they play sports, good support and pressure relief help them bounce back from practice. Teens also use a bed as a couch, so edge support that doesn't collapse when they sit on the side to lace up cleats or do homework is worth having as well. Growing pains are real, and a supportive surface that cushions sensitive joints can take the edge off at night.

The Practical Things Parents Forget

A few small moves protect the investment. Start with a waterproof protector from day one. It's cheaper than a new mattress and saves you from spills, accidents, and sick days. Aim to rotate their mattress head-to-toe every couple of months so it wears evenly. And if it's going in a bunk or trundle, check the height. You want a lower-profile mattress that sits well below the top of the guardrail, plus lower beds are safer for younger kids anyway.

When to Replace the One They Have

As a general rule, most mattresses are good for seven to ten years, sometimes less, under hard daily use from a kid. You can typically tell whether it's time to replace the one they have with the following signs:  

• Their feet hang off the end.
• You can see or feel sagging and body impressions.
• They've started complaining about being uncomfortable or waking up sore.
• They've hit a major growth spurt, and the old bed suddenly looks small.

Bring Them In and Let Them Try It

The part you can't do online is to have your kid lie down on it. Firmness is personal, and they're the ones sleeping on it. A teen can usually tell in about two minutes whether a bed feels right, and a younger kid will show you fast.

That's a lot of why families come into our mattress showroom in Denver. We'll ask how your kid sleeps, how big they are, and what the room and budget look like, then point you to options that fit without steering you toward the priciest bed on the floor. 

The brands we carry make firmer, durable models in twin, twin XL, and full sizes, with the kind of certifications you want in a kid's room. And when you find the one, delivery, setup, and haul-away of the old bed are included within 50 miles.

Frequently Asked Questions

What firmness is best for a child's mattress?

Younger, lighter kids need it firmer, around 7 to 8 out of 10, because they don't weigh enough to compress a soft bed and need the support while their spine is growing. School-age kids do well around medium-firm, and teens land around medium to medium-firm depending on their size and how they sleep.

What size mattress should I get for my teenager?

A twin works for younger or smaller teens in tight rooms, but most teens are more comfortable on a twin XL or full. A full is a smart buy for a kid about to hit a growth spurt, and if you have the space, a queen can carry them into early adulthood without another upgrade.

Are memory foam mattresses safe for kids?

Yes, as long as you check the certifications. Look for CertiPUR-US foam and GREENGUARD Gold for low emissions, both of which mean the materials have been independently tested. Air out any new mattress for a day or two before they sleep on it.

Is a firm or soft mattress better for a growing child?

Firmer is usually the safer bet, especially for younger kids. Support matters more than plushness while the spine is developing, and a too-soft bed lets the hips sink out of alignment. Older and heavier kids can handle a bit more cushion.

How often should I replace my kid's mattress?

When their feet hang off the end, the bed sags, they start complaining, or they've had a big growth spurt. Most mattresses last seven to ten years, though a kid's hard use can shorten that.

What's the best mattress for a teen who sleeps hot?

A hybrid with coils and a breathable cover sleeps cooler than dense all-foam. Cooling covers and gel-infused foams help too. Teens run warm through puberty, so breathability is worth prioritizing.

Can my kid use any mattress in a bunk bed?

No, height matters. The mattress should sit well below the top of the bunk's guardrail, so a lower-profile model is usually the right call. Measure the rail height before you buy.

 

Sleep Basil Mattress Co.

Walk-ins welcome, or book a 1:1 Sleep Consultation with the owners. 

6485 E Hampden Ave, Denver, CO 80222

Monday–Saturday: 10am–6pm Sunday: 12pm–5pm

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About the Author

Phil Lotterhos

Phil Lotterhos is a consultative mattress expert and co-owner of Sleep Basil, Denver's premier mattress store. With over 10 years of helping Colorado residents achieve better sleep, Phil formerly owned Urban Mattress Boulder and has become Denver's go-to local mattress guru. Known for his educational, easy-going approach and belief that "materials matter more than brand names" in mattress construction, Phil combines deep product knowledge with a passion for helping people find their perfect sleep solution. When not helping customers, he's an avid jazz pianist bringing the same attention to detail to both music and mattresses.