Mattress Firmness: What Every Sleep Type Needs to Know
There’s a particular kind of quiet that happens at 3 am when you’re lying in bed and your lower back wakes up before you do. You shift, you try the other side, and somewhere in that half-conscious negotiation you start wondering if the mattress is actually the problem.
Should you have gone softer? Firmer? Is medium firm actually medium? And what mattress firmness is best for the way you sleep?
It's a surprisingly important decision because the wrong mattress doesn't just affect your nights. It quietly follows you into your mornings, showing up as a sore back, stiff shoulders, restless sleep, or that familiar feeling of never quite waking up refreshed.
This mattress firmness guide explains the different mattress firmness levels, how they affect your sleep, and how to choose the right feel based on your sleeping position, body type, and lifestyle.
Why mattress firmness matters more than most people realise
Most of us spend around a third of our lives in bed. Yet when it comes to choosing a mattress, we're often distracted by fancy materials, cooling technology, or whatever happens to be on sale.
Firmness deserves just as much attention because it directly affects how your body rests throughout the night. It’s the difference between a mattress that works with your body and one that works against it.
What are the mattress firmness levels?
Mattress firmness refers to how much a mattress resists or yields to the weight and pressure of your body. A soft mattress lets you sink in noticeably. A firm one holds its shape and keeps you closer to the surface. It is not the same as support, although the two get confused constantly.
Although the exact rating can vary slightly between brands, the general guide looks like this:
| Mattress firmness level | Firmness scale | Mattress feel | Best for | Potential drawbacks |
|---|---|---|---|---|
| Soft | 1–3 | Plush, deeply cushioned with noticeable sinkage that hugs the body. | Side sleepers, lightweight sleepers, people who want maximum pressure relief around the shoulders and hips. | May allow too much sinkage for stomach sleepers or heavier individuals, which can lead to poor spinal alignment. |
| Medium-Soft | 4 | Soft with slightly more support than a plush mattress while still offering excellent contouring. | Lightweight sleepers, side sleepers who want pressure relief without feeling like they're sinking too deeply. | May still feel too soft for heavier sleepers or those who primarily sleep on their stomach. |
| Medium | 5 | Balanced comfort that combines gentle contouring with even support. | Combination sleepers, average-weight sleepers, those who switch sleeping positions throughout the night. | May feel too firm for sleepers seeking a plush feel or too soft for those who prefer maximum support. |
| Medium-Firm | 6–7 | Supportive with light cushioning that keeps the spine aligned while relieving pressure points. | Back sleepers, couples, combination sleepers, and most average-weight adults. | Some dedicated side sleepers may find it firmer than they prefer, particularly if they're lightweight. |
| Firm | 8–10 | Minimal sinkage with a stable, elevated sleeping surface. | Stomach sleepers, heavier sleepers, and people who prefer sleeping "on" rather than "in" the mattress. | Can create pressure points for side sleepers or lightweight individuals if there's insufficient cushioning. |
While every brand may interpret the scale slightly differently, these ratings provide a useful benchmark when comparing mattresses.
Mattress firmness guide by sleep position
One of the simplest ways to narrow down the types of mattress firmness is by considering how you sleep.
Best mattress firmness for side sleepers
Side sleeping places significant pressure on the shoulders and hips, so a mattress that's too firm can create uncomfortable pressure points.
Most side sleepers benefit from:
Soft to medium mattresses (3-5)
Excellent pressure relief
Gentle contouring around the shoulders and hips
If you frequently wake up with sore shoulders or tingling arms, your mattress may simply be too firm.
Best mattress firmness for back sleepers
Back sleepers need a careful balance between cushioning and support. The mattress should cradle the lower back while preventing the hips from sinking too deeply.
Most back sleepers sleep comfortably on:
Medium to medium-firm mattresses (5-7)
Best mattress firmness for stomach sleepers
Stomach sleeping places the greatest demand on spinal alignment. If the hips sink too far, the lower back arches uncomfortably throughout the night.
Most stomach sleepers should consider:
Medium-firm to firm mattresses (6-8)
Best mattress firmness for combination sleepers
If you change positions throughout the night, look for a mattress that's responsive enough to adapt as you move without making you feel trapped.
Combination sleepers can consider:
Medium to medium-firm mattresses (5-7)
How body weight affects mattress firmness
Here's something many mattress guides overlook: firmness isn't universal. The same mattress can feel completely different depending on who's sleeping on it.
Lightweight sleepers (under 60kg): Lighter sleepers don't compress the mattress as deeply. A medium mattress may feel considerably firmer than intended, making softer options more comfortable.
Average-weight sleepers (60-100kg): Average-weight individuals generally experience the mattress as designers intended. Most firmness recommendations are based on this weight range.
Heavier sleepers (over 100kg): Heavier sleepers naturally compress the comfort layers more deeply. A mattress marketed as medium may feel noticeably softer, making medium-firm or firm models better suited for maintaining support over time.
What mattress firmness is best for couples?
Shopping for one person is hard enough. Shopping for two often feels like negotiating thermostat settings. If you and your partner have different sleep preferences, start by looking at your shared needs.
Consider:
Your primary sleep positions
Your combined body weights
Whether one of you moves frequently during the night
Whether motion isolation is important
For many couples, a medium-firm mattress provides the best compromise because it offers broad comfort across different body types and sleeping styles.
Some mattresses also feature advanced comfort layers that respond individually to each sleeper, helping both partners feel properly supported without constantly disturbing one another (like our Ayrie Mattress).
Mattress firmness vs mattress support: They're not the same thing
A firmer mattress isn't automatically more supportive. Support comes from the mattress core, which keeps your spine aligned. Firmness comes from the comfort layers, which determine how the mattress feels.
Imagine sitting in a well-designed ergonomic chair. The seat might feel soft, but your posture is still well supported because of the chair's structure. The same principle applies to mattresses.
How to choose mattress firmness
If you're still wondering how to choose mattress firmness, don't focus on firmness alone. Instead, consider how all the pieces fit together.
Ask yourself:
What's my primary sleeping position?
How much do I weigh?
Do I sleep hot?
Do I share the bed?
Do I usually wake with aches or pressure points?
Do I prefer feeling "in" the mattress or "on" the mattress?
Your answers will usually point you towards the right firmness before you even start comparing mattresses. Rather than choosing the firmest or softest option, focus on one that keeps your body comfortable and your spine properly aligned.
Find your comfort sweet spot
Finding the right mattress firmness isn't about choosing the softest or firmest option. It's about finding the balance between comfort and support for the way you sleep.
After all, we don't just spend a third of our lives in bed. We recover, recharge, and prepare ourselves for the day ahead. The right mattress won't solve every restless night, but it can become the foundation for better sleep and better mornings for years to come.
Frequently asked questions about mattress firmness
What are the mattress firmness levels?
Most mattresses are rated on a scale of 1 to 10, ranging from very soft to extra firm. The most common options fall between medium (5) and medium-firm (6-7), which suit a broad range of sleepers.
Do mattresses become softer over time?
Yes. Most mattresses soften slightly as the comfort layers break in through regular use. This is a normal part of the bedding-in process and shouldn't dramatically affect support if the mattress is well made.
Is a firm mattress better for back pain?
Not necessarily. Many people with back pain benefit more from a supportive medium-firm mattress than an extra firm one. Proper spinal alignment matters more than firmness alone.
