How to Make a Mattress Firmer or Softer

"This mattress feels wrong" is one of the most common complaints in sleep, and it usually gets answered with a shopping trip — a topper, a mattress pad, sometimes a whole new frame. Before you spend money on any of that, it's worth ruling out the two things that have nothing to do with a topper or a base swap. Rule out break-infirst — new foam is genuinely stiffer than it will be in a month, and a lot of "too firm" complaints resolve themselves with time and body heat, no purchase required. Then rule out a real firmness mismatch— if the bed is the wrong feel for your body, no amount of topper or plywood turns a firm mattress into a soft one, and the honest fix is the sleep trial, not a patch job you'll be maintaining for years. Once those two are off the table, here's what actually works to nudge a mattress softer or firmer, and what each fix can and can't realistically do.

Rule These Out First

A brand-new mattress feels different on night one than it will after a few weeks of regular sleep. Memory foam and polyfoam are stiffer straight out of the box — they've been compressed, rolled, and shipped, and the cell structure needs time and repeated body heat to relax into its intended feel. Latex and hybrid beds go through a milder version of the same process. Judging a mattress in its first few nights is judging it at its firmest, which is exactly why so many "too firm" complaints show up in week one and quietly disappear by week four. If your bed is new, give it the full break-in period before you decide anything needs fixing. Buying a topper to fight a firmness that was already going to soften on its own is money spent solving a problem that was solving itself.

If you're past that window and it's still off, ask a second, harder question: is this actually the wrong firmness for you, rather than a fixable surface issue? A topper can shift the feel by a level or so — soft to medium-soft, firm to medium-firm. It cannot turn a genuinely firm mattress into a genuinely soft one, or the reverse, because the mattress underneath is still doing most of the work of holding you up. That's not a surface problem you can layer your way out of, it's a firmnessproblem, and the honest fix is the sleep trial and an exchange rather than years of compensating for a bed that was never right for your body in the first place. Most mattress brands sell precisely because of this gap between how a bed feels in a showroom and how it feels after thirty nights — the trial exists to let you correct a real mismatch cheaply, while it's still an option. Everything below works well on a mattress that's close but not quite there. None of it rescues one that's fundamentally the wrong pick.

How to Make a Mattress Softer

The single most effective fix, by a wide margin, is a plush memory-foam or latex topper. It sits directly under your sheet and gives you a fresh few inches of contouring and pressure relief before you ever reach the firmer mattress underneath — which is exactly why it moves the needle more than anything else on this list. A soft or medium-soft memory-foam topper, roughly two to three inches thick, is the version most people reach for; a soft latex topper does something similar with a bouncier, less "stuck" feel for anyone who dislikes the slow sink of foam. Our mattress topper roundup breaks down which materials and thicknesses soften a bed the most, and which ones undersell it.

• Warm the bedroom up.Memory foam is genuinely temperature-sensitive — it softens and contours more as it warms, and firms up noticeably in a cold room. A slightly warmer bedroom, a mattress warmer, or simply sleeping under more covers makes a foam mattress feel more plush without touching the bed itself. It's a small effect on its own, but it stacks with a topper rather than competing with it.
• Give it the full break-in period.Worth repeating here specifically for softness: a lot of "too firm" mattresses are just new ones that haven't relaxed yet, and buying a topper before that window closes means you may end up with a mattress-plus-topper combination that's softer than you actually wanted once the mattress itself finishes settling in.
• Add a thick, fluffy mattress pad.Not as dramatic as a topper, but a quilted pad with a generous fill adds a lighter, softer touch on top of the sheet layer — a smaller move for a smaller gap, and a reasonable first step if the mattress is only slightly firmer than you'd like rather than clearly wrong.
• Use the softer side, if you have one.A genuinely flippable two-sided mattress sometimes has a softer comfort layer on one face and a firmer one on the other. Most mattresses made in the last couple of decades aren't built this way — flipping a one-sided mattress just exposes the support core with no comfort layer at all, which makes things worse, not better — but if yours is a genuine two-sided design, it's a free option worth checking before you buy anything.

How to Make a Mattress Firmer

Firming up a bed usually starts underneath it, not on top of it. A too-flexible or wide-slatted baselets a mattress flex and sink more than it's designed to, which reads as a softer — sometimes even saggy — feel that has nothing to do with the mattress itself. This is easy to miss because it looks exactly like a mattress problem from on top of the bed. A bunkie board or a sheet of plywood between the mattress and the base removes that give and turns a flexible foundation into a solid, continuous one. It's often the single biggest lever available, and it's the one people skip because it doesn't look like a mattress fix — check the base before you spend money assuming the mattress itself is the issue.

• Add a firm topper.It sounds backwards, but yes — a firm, high-density foam or latex topper adds a denser surface layer on top of a mattress that feels too soft, which changes what you sink into before you ever reach the mattress's own comfort layer. Latex holds up especially well here: Dunlop latex in particular is denser than Talalay, which makes it a common pick when the goal is specifically a firmer, more supportive surface rather than more cushioning.
• Put the mattress on the floor, temporarily.A hard, flat surface reads firmer than any slatted frame, because there's no give anywhere in the support — the whole surface of the mattress is resting on something rigid instead of a series of slats with gaps between them. It's not a permanent setup for most people, and it comes with its own downsides like airflow and moisture, but it's a fast, free way to test whether the base was actually part of the problem before you buy a bunkie board.
• Keep the room cooler. The mirror image of the softening advice — foam firms up in a cooler room and softens in a warm one, so if your bedroom runs warm, especially overnight, that alone may be adding more softness than you realized. This matters more for all-foam beds than for innerspring or hybrid mattresses, where coils do most of the support work and are far less temperature-sensitive than foam.

The Honest Limits

A topper is a real fix, not a placebo — but it's a tweak, and it's worth being honest about what it can't do. It can shift a mattress's feel by a level or so, which is genuinely enough to turn an uncomfortable bed into a workable one in plenty of cases. What it can't do is transform a bed that's genuinely the wrong firmness for your body, because the mattress underneath is still the mattress underneath, doing most of the structural work every night. It also can't fix a mattress that's actually sagging or worn out underneath — a soft topper over a collapsed support core just hides the dip for a while instead of solving it, and can actually make spinal alignment worse by adding softness on top of a surface that has already lost its support. The same logic applies to a firm topper over a base that's genuinely broken: it adds density on top, but the flex underneath is still there.

If you've checked the base, given the mattress its full break-in period, and tried the right topper, and it's still noticeably wrong for you, that's the signal to stop patching and start thinking about the bed itself rather than another layer on top of it. Most mattresses ship with a sleep trial specifically for this reason — a window of thirty, sixty, or a hundred-plus nights that exists precisely because firmness preference is hard to judge from a showroom or the first few nights at home. Using that trial to exchange or return a bed that's genuinely off is a better outcome, financially and physically, than years of compensating for it with toppers, pads, and plywood that were never going to solve a mismatch they weren't designed to fix.