How firm should your mattress be?

Firmness is the first thing a mattress page tells you and the least standardised number on it. One brand’s medium-firm is another brand’s firm, there is no published test that settles the difference, and you are usually buying without lying on it first. This guide is about reading those labels for what they are worth, narrowing the field to one or two candidates, and then letting the sleep trial make the actual decision.

Everything below comes from what the brands publish — specifications, firmness ratings, trial terms and warranty documents. We do not buy these mattresses and sleep on them, so nothing here is a report on how one feels in a bedroom.

Firmness is a feel, not a measurement

There is no industry standard behind the word. Foam can be measured for indentation load, but brands rarely publish those figures, and in a hybrid the feel is set by the comfort layers, the gauge and height of the springs, and even the cover — not by one number that survives comparison between makers. Two mattresses both sold as medium-firm can sit a full point apart on the ten-point scales the brands themselves use.

Firmness is also not the same thing as support. Firmness is how the surface feels in the first few seconds; support is whether the mattress holds your spine in roughly the line it holds when you are standing. A soft-feeling mattress over a strong core can be very supportive, and a hard one over a weak core can still let your hips sag. We go through that distinction in detail on the best mattress for back pain page.

The ten-point scale, and where the market actually sits

Rating	Usually labelled	Feels like
1–3	Plush / soft	You sink in; the surface wraps around the shoulder and hip
4–5	Medium-soft	Noticeable give, still a surface under you
6–7	Medium-firm	The most common answer in Australia; slight give, then it holds
8–10	Firm / extra firm	Very little give; you lie on top rather than in it

Boxed mattresses cluster at six to seven because that is the safest single answer when the buyer cannot try it in a shop. It is worth knowing how narrow that band is: of the eleven mattresses we rank, only five are sold as one fixed feel — the Newentor Hybrid (medium firm), the Newentor Hybrid Pro (medium-soft), the Emma Luxe ViscoCool (medium-soft), the Origin LumbarCloud (medium-plush) and the TEMPUR Ease 20 (medium). The other six give you more than one option, which we come back to below.

Start with the position you sleep in

• Side sleepers. Your shoulder and hip need somewhere to go. Too firm and they cannot sink, so all your weight rests on two points — that is the numb arm and the sore hip in the morning. Medium-soft to medium usually suits.
• Back sleepers. You need the gap at your lower back filled without your hips dropping below your ribs. Medium to medium-firm is the usual range.
• Stomach sleepers. The hips must not sink, or your lower back arches all night. Firm, and be suspicious of thick soft toppers.
• Combination sleepers. Choose for the position you start the night in and spend the most time in. If that is genuinely split, medium-firm is the compromise that fails least often.

If you share the bed and you and your partner sleep in different positions, do not average the two. Look instead at the mattresses that let each side be set differently, or at ones you can change later.

Then adjust for your body weight

Firmness labels are written for someone in the middle of the range. Your weight decides how far into the mattress you actually get, so the same model can be two different beds for two different people.

• Under about 60 kg. You compress the comfort layer less, so most mattresses feel firmer than the label suggests. Consider one step softer.
• About 60–90 kg. The labels mean roughly what they say.
• Over about 90 kg. You press through the comfort layer into the support core, so the same mattress feels softer than the label. Consider one step firmer, and pay more attention to what the core is made of than to the top few centimetres.

A large weight difference between two people in the same bed is the classic case for a mattress with separate firmness per side, or springs that move separately enough that one person’s movement does not travel across.

If you are stuck between two, buy the one that can change

Firmness is the specification most likely to be wrong on arrival, so a mattress that can be adjusted is worth real money at the point of choosing. Six of the eleven mattresses we rank offer more than one feel:

• Sleeping Duck Mach II — medium, firm, or one of each side.
• Origin Hybrid Pro — medium-firm or firm.
• Onebed Original 11″ — medium or medium-firm.
• Ecosa — three settings.
• Koala — flippable, medium-firm on one face and firm on the other.
• Sealy Posturepedic Exquisite Rosewood — sold in four comfort levels, from firm through to ultra plush.

There is a difference worth catching in that list. Sealy’s four levels are a choice you make at the checkout — they are different models, and changing your mind later means returning the mattress. The other five change after it arrives, by rearranging or swapping internal layers or by turning the mattress over. What is involved differs by brand, so read the maker’s own instructions before you count on it. Every firmness option each of them lists is on our side-by-side comparison.

How to tell you got it wrong

Give it time first. A new mattress softens slightly over the first few weeks and your body adapts to it at the same time, which is why most brands ask you to sleep on it for a minimum number of nights before they will accept a return. Judging on night three tells you very little.

• Too firm tends to show up as pressure: a numb arm, a sore shoulder or hip, waking often to change position, or a sense that only two parts of you are actually touching the bed.
• Too soft tends to show up as a lower-back ache that is worst on waking and eases after half an hour of moving around, along with a feeling of being stuck when you try to roll over.

One caveat: pain that does not follow that pattern, or that does not shift after a fair trial on a mattress that suits your position and weight, may not be about the mattress at all. This is a comparison site, not medical advice. If your back pain is persistent, severe or new, see a health professional before you spend money on a bed.

The trial period is where the decision actually gets made

Since no specification can tell you how a mattress will feel to you, the trial terms are the part that protects you. Among the nine we rank, seven publish a sleep trial, ranging from 100 to 150 nights. The TEMPUR Ease 20 states that it has no sleep trial. The Sealy Posturepedic Exquisite Rosewood does not state one either way, which is not the same as saying there is none — ask the retailer before you buy.

When you read the terms, three things matter more than the headline number:

• The minimum. Most trials cannot be started until you have slept on it for a set number of nights.
• Who pays for the return. Free pick-up, a flat fee and a restocking charge are three very different outcomes.
• Refund or exchange. Some brands return your money; others will only swap the mattress or the firmness layer.

And keep the two terms apart: a warranty is not a trial. The warranty covers manufacturing faults and sagging deeper than a stated depth, usually for ten years or more. It will not help you if the mattress is simply the wrong feel. That is what the trial is for, and it is why we score the two separately — see how we rate.

The short version

• Pick your range from the position you sleep in, then move one step for your weight.
• Treat the label as the brand’s opinion, not a measurement. Compare within a brand, not across brands.
• When two options both look right, take the one whose firmness can be changed later.
• Read the trial minimum, the return cost and whether it is a refund or an exchange — before you read the trial length.
• Give it three to four weeks before you judge it.