Firm or soft is the question almost everyone asks first, and it's the one most likely to lead to a bad purchase. Not because the answer is complicated, but because the question is slightly wrong. Firmness is not a quality rating. There is no "better" end of the scale, and the mattress that feels wonderful for ten minutes in a showroom is frequently the one that has you waking up sore three months later.
This guide covers what firmness actually is, how it differs from support, which level suits your body and sleeping position, and how to tell when you've got it wrong.
The Short Answer
Most adults sleep best on medium to medium-firm. That is not a cop-out, it's where the majority of body types and sleeping positions overlap.
From there, adjust in two directions. Softer if you sleep on your side, weigh less than about 60 kg, or feel pressure building in your shoulders and hips. Firmer if you sleep on your stomach, weigh more than about 90 kg, or wake up with lower back ache.
If you're between those descriptions — and most people are — start at medium-firm. It is the level that disappoints the fewest people, and the one you're least likely to regret.
"Firmness is not a quality rating. A firm mattress is not a better mattress, it's a different mattress. The only question is which one keeps your spine neutral."
Firmness vs Support: The Distinction That Fixes Most Bad Purchases
These two words get used interchangeably in shops and they mean entirely different things. Getting them confused is behind a large share of mattress regret.
Firmness is how the surface feels. It's the immediate sensation when you lie down — plush, medium, firm. It's subjective, it's about the top few centimetres, and it's what you notice in the first thirty seconds.
Support is whether the mattress holds your spine in a neutral line. It's structural, it comes from the core underneath, and you don't notice it at all until you wake up.
The important consequence: a soft mattress can be extremely supportive, and a firm mattress can be badly unsupportive. A plush comfort layer over a dense, well-built core will cradle your shoulders while keeping your hips level. A cheap firm foam slab with no structure underneath will feel rigid and still let you sag in the middle within two years.
So when someone tells you they need "a firmer mattress for their back", what they usually need is better support. Those are often solved by different mattresses — and what the core is made of decides which, as our guide to mattress types sets out.
The Firmness Scale in Plain Terms
Most manufacturers use a 1–10 scale. It isn't standardised between brands — one company's 6 is another's 7 — but the relative positions are consistent enough to be useful.
| Level | Feels like | Typically suits |
|---|---|---|
| 1–2 — Very soft | Deep sink, enveloping | Rarely recommended; too little support for most adults |
| 3–4 — Soft | Noticeable contouring at shoulders and hips | Lighter side sleepers under ~60 kg |
| 5–6 — Medium | Balanced; some give, clear support underneath | Side sleepers, combination sleepers, average build |
| 6–7 — Medium-firm | Mostly on top of the mattress, slight contouring | Back sleepers, most adults, couples |
| 8–9 — Firm | Very little sink, lifted feel | Stomach sleepers, heavier sleepers over ~90 kg |
| 10 — Very firm | Almost no give | Niche; usually specific medical direction |
Scales vary between manufacturers. Always ask what a given number means in practice rather than comparing numbers across brands.
Why the Same Mattress Feels Different to Different People
Here is the part that surprises people: firmness is not a fixed property of the mattress. It is the result of an interaction between the mattress and your body.
A 55 kg sleeper compresses a mattress far less than a 95 kg sleeper. Same mattress, same materials — the lighter person experiences it as firm, the heavier person experiences it as medium. Neither is wrong. This is why online reviews contradict each other so violently.
| Body weight | How firmness reads | Usually needs |
|---|---|---|
| Under 60 kg | Everything feels firmer than rated | Softer than you'd expect — 4–6 |
| 60–90 kg | Roughly as rated | Medium to medium-firm — 5–7 |
| 90–110 kg | Everything feels softer than rated | Medium-firm to firm — 7–8 |
| Over 110 kg | Significantly softer than rated | Firm, with a high-density core — 8+ |
For heavier sleepers there's a second consideration beyond feel: durability. More body weight means more compression per night, so core density matters as much as the firmness rating. A medium-firm mattress with a weak core will soften into the wrong firmness within a couple of years, which is a support failure disguised as a firmness problem.
Firmness by Sleeping Position
Position determines where your body weight concentrates, and therefore where the mattress has to give and where it has to hold.
Side Sleepers
On your side, your shoulder and hip carry almost all of your body weight across two narrow contact points. Those points need to sink into the mattress so your spine can stay straight from neck to tailbone.
Too firm and your shoulder can't drop, so your spine bends sideways all night — that's the source of the shoulder ache and hip pressure side sleepers complain about. Too soft and your torso sinks further than your shoulders, bending the spine the other way. More detail in choosing a mattress for side sleepers.
Back Sleepers
Lying on your back, weight distributes over a much larger area, so you need less give overall. What you do need is for the mattress to fill the gap under your lower back while stopping your hips from dropping.
Too soft and the hips sink, exaggerating the lumbar curve and compressing the lower back over eight hours. Too firm and there's an air gap under the lumbar arch, leaving those muscles working all night to bridge it.
Stomach Sleepers
Stomach sleeping starts at a disadvantage: your neck is rotated for hours and your pelvis is the heaviest thing in contact with the surface. If the hips sink even slightly, the lower back arches into hyperextension, which is exactly what produces that stiff, sore morning.
Firm is not optional here. You want to lie as close to level as possible. A thinner pillow helps too — a high pillow adds neck extension to a position that already has plenty. The full case is in why stomach sleepers need firmer mattresses.
Combination Sleepers
If you move between positions during the night, you need a mattress you can move on. Deep-contouring surfaces create a hollow you have to climb out of every time you turn, which fragments sleep even when you don't fully wake.
Medium-firm with a responsive material is the answer. Responsiveness matters as much as the number here — a mattress that rebounds quickly lets you change position without effort.
What Firmness Does to Spinal Alignment
Everything above is really in service of one thing: keeping your spine in the position it holds when you stand up straight. Neutral means the natural inward curve at the neck, the gentle outward curve of the upper back, and the inward curve at the lower back are all preserved while you lie down.
When a mattress is too soft
The heaviest parts of you — hips and torso — sink further than the rest. The spine sags into a hammock shape. Lower back muscles spend the night compensating, and the classic symptom is stiffness on waking that eases after ten or fifteen minutes of moving around.
When a mattress is too firm
The surface refuses to accommodate your natural curves. Shoulders and hips take concentrated pressure because they can't sink, and gaps open under the lumbar curve and the waist. The spine may look straight but is unsupported along its length, so muscles stay engaged rather than releasing. Symptoms tend to be pressure points and numbness rather than aching.
When firmness is right
Heavier areas are held up, lighter areas are met by the surface, and nothing is working. You tend to move less during the night, and you wake without needing to loosen up first.
Note that this is achieved through balance, not rigidity. Firmness contributes to alignment but doesn't create it on its own — the core underneath and the material itself matter just as much, which is covered in our mattress buying guide.
Signs Your Firmness Is Wrong
Your body reports the problem before you consciously notice it. The pattern of the symptom tells you which direction to correct in.
Too soft — the tell-tale signs
- Lower back stiffness on waking
- Stiffness eases after moving around
- Feeling of rolling toward the middle
- Effort required to change position
- A visible dip where you sleep
- Worse after a long night, not better
- Partner disturbance when either moves
- Feeling hot — more contact, less airflow
Too firm — the tell-tale signs
- Sore shoulders or hips, not back
- Numbness or pins and needles in an arm
- Frequent position changes at night
- Pressure points that ache in bed
- Better sleep on a sofa or in hotels
- Gap you can feel under your lower back
- Waking specifically on the contact side
- Relief from adding a topper
One diagnostic that cuts through most of this: if the pain is worst on waking and improves as you move, suspect too soft. If the pain builds while you're lying in bed and eases once you're up, suspect too firm. Where back pain specifically is the symptom, choosing a mattress for back pain relief goes further.
And if the symptoms don't match either pattern cleanly, the issue may be the mattress's age rather than its firmness — a mattress that has lost its support behaves like a soft one regardless of what it was rated when you bought it. Our guide to 8 signs it might be time to replace your mattress covers how to tell the difference.
Firmness and Temperature
An angle most firmness guides skip, and one that matters more in a tropical climate than anywhere else.
Softer mattresses let more of your body sink below the surface, which increases contact area and reduces airflow around you. The same contouring that relieves pressure also traps heat. Firmer surfaces keep more of you above the mattress with air circulating around your sides.
It's a secondary effect — material and cover do far more for temperature than firmness does — but if you're on the fence between two levels and you sleep hot, it's a reasonable tiebreaker in favour of the firmer one. We cover the material side properly in choosing a mattress for hot and humid climates and in latex vs memory foam.
When Two People Want Different Firmness
Extremely common, and it has better solutions than "compromise on medium and both be slightly unhappy."
If the gap is small — one wants medium, the other medium-firm — go with the firmer preference and add a topper on the softer sleeper's side. Softening a firm mattress is straightforward; firming up a soft one is not.
If the gap is large — soft versus firm — a single fixed-firmness mattress will not satisfy both of you, and pretending otherwise wastes money. Look for a mattress with adjustable internal layers that can be set differently on each side.
If one of you is much heavier, remember the same mattress already feels different to each of you. The lighter partner may need less softness than they think, because they're experiencing the surface as firmer anyway.
How to Actually Test Firmness
Ten minutes in a showroom is worth something, but not much. Here's how to get more out of it, and what to do afterwards.
Lie in your real sleeping position. Not on your back because it's polite. If you sleep on your side, lie on your side, with a pillow of roughly the height you use at home.
Stay there for at least ten minutes. Pressure points take time to announce themselves. The first thirty seconds tell you almost nothing except whether it's plush or firm.
Do the hand test. Back sleepers: slide a hand under the lumbar curve. Side sleepers: have someone check whether your spine is horizontal.
Then allow 30 days at home. New mattresses genuinely change. Latex and foam need time to fully decompress, and your body needs time to unlearn the compensations it developed on your old mattress. Judging a new mattress in week one is the single most common reason people return one that would have suited them.
This is why a trial period matters more than a showroom. Lazy Lowie's runs to 100 nights, with a minimum 30-day settling-in requirement built in for exactly this reason — full terms are in the warranty and returns policy.
Adjustable Firmness
The underlying problem with fixed firmness is that it assumes your needs never change. They do. Body weight shifts, injuries happen, pregnancy changes everything, and the position you sleep in at forty may not be the one you slept in at twenty-five.
Mattresses with adjustable internal layers let you re-tune firmness without replacing the mattress. It's a meaningful practical advantage over a ten-year lifespan, and it removes the single biggest risk in buying online — that you guess the level wrong and are stuck with it.
The Lazy Lowie Original Mattress is built this way: you choose your firmness at order, and the internal layers can be reconfigured later if your needs change. Available in 20, 25 and 30 cm across all seven Indonesian sizes — pricing for each is in the 2026 Bali price guide.
Frequently Asked Questions
Is a firm mattress better for back pain?
Not necessarily, and this is the most persistent myth in mattress buying. Research generally points to medium-firm as the better choice for lower back pain, not firm. A too-firm mattress leaves the lumbar curve unsupported, which can make things worse. What matters is neutral spinal alignment, not maximum rigidity.
What firmness is best if I sleep in every position?
Medium-firm, around 6, with a responsive material. Combination sleepers need to be able to move easily, so responsiveness matters as much as the firmness level. Deep-contouring surfaces make repositioning harder and fragment sleep.
Can I make a firm mattress softer?
Yes — a latex or foam topper adds a softer comfort layer without changing the support underneath. The reverse doesn't work: nothing you put on top of a too-soft mattress will restore support to the core.
How long before a new mattress feels normal?
Around 30 days. The mattress finishes decompressing and your body adapts away from the compensations it learned on your old one. It's genuinely common for a correctly-chosen mattress to feel wrong in week one.
Does firmness change over time?
Yes. All mattresses soften with use, which is normal wear rather than a defect. What isn't normal is sagging — most warranties, including ours, treat visible indentations deeper than 4 cm as structural failure rather than break-in softening.
Choose Your Firmness, Change It Later
The Original Mattress is built with adjustable internal layers, so you pick your firmness at order and can re-tune it as your needs change. Seven sizes, three thicknesses, 100-night trial.
Explore the Original Mattress →Firm or Soft? Neither. Correct.
The firmness question only has an answer once you add your body weight, your sleeping position and what your mornings currently feel like. Medium-firm is where most adults land. Side sleepers and lighter people move softer, stomach sleepers and heavier people move firmer.
Keep the distinction between firmness and support in mind while you shop, because it's the one that stops you buying a rigid mattress when what you needed was a well-built one.
And give any new mattress thirty days before you judge it. Your back has habits too.