How To Choose The Right Degree Of Firmness

How To Choose The Right Degree Of Firmness - UK Guide (2024)

Last updated: 31.10.2023 Reading time: 9 Min.

You may know that you like your mattress to be as soft and fluffy as a cloud ... or as firm and stable as a table.

But what exactly does this mean? And how can you translate these vague descriptions into a universally comprehensible firmness scale?

That's exactly what we'll be looking at in this article, walking you through what mattress firmness relates to, how firmness scales are created, and helping you choose the right degree of firmness for your next mattress.

There's lots to cover, so let's get to it 👇

Firmness Scales

What is a firmness scale?

The firmness of a mattress describes - as the name suggests - how soft or firm a mattress feels.

This could be soft and fluffy like a cloud (or, at least, what we all imagine when we think about diving into a cloud) or as hard as a table 🌥

Differences in mattress firmness are caused by the use of different materials and their respective densities.

Unfortunately, there is no uniform industry standard for a mattress's firmness rating.

And this is where the confusion sets in.

Some brands use terms like H2, H3, and H4. Others simply describe their mattresses as 'softer' or 'firmer'. And others, again, refrain from specifying any degree of firmness and call their mattresses one-fits-all universal types of medium firmness.

How are we supposed to make sense of that? 🤔

Don't worry; we came up with a grand solution, which we dive into further below.

For now, it's important to remember that there are different types of mattresses.

Soft mattresses

These are generally memory foam mattresses with lots of body-contouring support, cushioning and extra padding.

They are popular with people looking for superior comfort and relaxation and give you that sleeping-on-a-cloud feeling.

You'll often find mattresses that have an upper comfort layer of memory foam to provide extra squishiness.

Medium-firm mattresses

These are the perfect in-between, mattresses that are not too soft and not too firm.

Medium-firm mattresses will suit most people.

We could describe these as your marshmallow mattresses: still soft and squishy, but with a lot more firmness than a cloud.

Firm mattresses

Firm mattresses generally offer high levels of support and durability.

They are well-suited to athletes and people struggling with back pain and tension.

These are your sleeping-on-a-table mattresses, but, of course, there are also various levels here and not all tables are hard as concrete.

Creating a firmness scale

There are many factors that can influence how firm a mattress feels and, as we've just discovered, you can't always rely on a brand to give you an exact degree of firmness.

This is why we've created the Sleep Hero firmness scale.

We've found this especially useful for bed-in-a-box mattresses 📦

As you'll be buying your mattress online, you can't rely on the general feel of a mattress as you would if you were buying from a traditional brick-and-mortar retailer.

We use our firmness scale in all our mattress reviews and buying guides to help you figure out which is the perfect mattress for you.

Why is the right degree of firmness so important?

Choosing the right degree of firmness is important for healthy spinal alignment 📏

If your chosen mattress is too firm, then your body will be forced to remain unnaturally straight, resulting in a misalignment of the spinal column.

On the flip side, if your mattress is too soft, you'll sink into the mattress too deeply, resulting in a hollow back.

In both cases, your spine will be misaligned, which can lead to tension and lower back pain.

Your sleep will also be impacted and you'll be far less comfortable.

If you choose the right mattress with the right degree of firmness, though, your body will sink in at the centres of gravity (i.e. your shoulder and pelvis) but remain well-supported everywhere else.

This allows your spine to remain straight throughout the night, easing tension and allowing for a comfortable night's rest.

Choosing the right degree of firmness, then, is essential for a good night's sleep 😴

What must a good mattress be able to do?

A good mattress must relieve pressure and support the body.

It cushions the entire body while supporting the hips and spine. The shoulders, pelvis and hips must sink in so the body is evenly balanced.

walter braun sleep expert
Walter Braun [1]

Sleep Expert

If you already struggle with severe back, neck, or joint pain, it's even more important to be aware of firmness levels and choose a mattress with the right level of support.

We'd strongly recommend choosing a mattress that meets orthopaedic requirements.

But what about stability?

Even though we refer to firmness as "the factor that determines how well you're supported", there is a deeper aspect that you need to pay attention to.

It's important to note the difference between firmness and stability.

People often assume that a firm mattress is necessary to keep your spine straight and that a soft mattress will automatically lead to back pain.

This isn't necessarily true.

A firm mattress can result in back pain if it's not the right fit for you.

Similarly, a soft mattress can have excellent stability and be perfect for you.

You always need to choose a mattress with good stability. All of the ones we recommend offer good stability and support.

Firmness can be a matter of personal preference.

But your build, weight, and height will impact which degree of firmness is best for you to ensure that the mattress you choose can support your body.

Spinal alignment

How to find the right degree of firmness

Even if you have a mattress that offers good overall support and stability, you still need to find a mattress with the right degree of firmness for you.

General sleeping preferences and your sleeping style may play a role, but the most important factors to consider include your weight, height, and preferred sleeping position 🤸‍♀️

You should consider the following general guidelines when choosing the right degree of firmness:

  • The heavier or larger you are, the firmer your mattress should be.
  • Side sleepers and lighter-weight people often require softer mattresses than back and stomach sleepers.
  • Conversely, back and stomach sleepers require firmer mattresses.
  • Your height also plays a role. If you are very tall, you may require a firmer mattress.

Degree of firmness according to bodyweight

Bodyweight is a decisive factor when selecting the right degree of firmness 🏋️‍♀️

But, since you also need to consider height, build, and prefered sleeping position, we can only give general guidelines and you still need to consider everything on a case-by-case basis.

The following table may help you decide which degree of firmness is right for you:

Degree of firmness Feeling Recommended bodyweight
H1 Soft Up to 60 kg (132 lbs)
H2 Soft to medium-firm 60 - 80 kg (132 - 176 lbs)
H3 Medium-firm 80 - 100 kg (176 - 220 lbs)
H4 Firm From 100 kg (220 lbs)
H5 Extra-firm From 130 kg (286 lbs)
No information (one-fits-all) Varies, mostly medium-firm See our mattress reviews

Degree of firmness according to sleeping position

Your sleeping position also greatly impacts which degree of firmness will be right for you.

Side sleepers

With side sleepers, only a few parts of the body touch the mattress.

This means that your entire body weight is focused at these points, putting an enormous amount of pressure on the mattress and creating distinct pressure points.

Side sleepers should choose slightly softer mattresses.

These allow your hips and shoulders to sink into the mattress much more deeply, keeping the spine in a healthy alignment.

Stomach and back sleepers

Front sleepers and back sleepers can afford to choose slightly firmer mattresses.

In both of these sleeping positions, sleepers need more support to keep their hips lifted and prevent the formation of a hollow back.

Firmness according to sleeping position

The right degree of firmness for couples

Couples should pay special attention to the degree of firmness before buying a mattress.

This is simply because not every degree of firmness will be equally suitable for both partners 👩‍❤️‍👨

In general, we'd recommend sticking to medium-firm mattresses and making use of risk-free trial periods to make sure both partners sleep comfortably.

If you and your partner are of largely varying heights or body weights, though, you may need to make a different plan.

Two single mattresses

One option would be to buy two single mattresses that are the same height but have different degrees of firmness.

In this way, each mattress will be perfect for each individual, ensuring that both partners can sleep well.

You can always buy a bed bridge to get rid of the little gap between the two mattresses.

Customisable mattresses

You could also invest in a customisable mattress.

These are mattresses that offer different degrees of firmness on each side of the mattress so that each half can be individually adjusted.

This is ideal but can be a little more expensive.

The right degree of firmness for children

Firmness is also important to consider when buying a mattress for your child.

While children over the age of 6 can sleep quite comfortably on adult mattresses, babies, toddlers, and small children under 6 generally require a special cot mattress.

These offer the perfect medium-firm feel to support growth and healthy bone development.

If a child's mattress is too soft or too firm, there is a risk of spinal deformities developing - especially at an early age.

Teenagers can orient themselves according to more general firmness scales.

The Sleep Hero firmness scale

If you've already browsed through our mattress reviews, you'll undoubtedly have come across references to the Sleep Hero firmness scale.

We've decided to create our own firmness classification system as it allows us to more easily compare mattresses to each other.

Plus, considering how inconsistent conventional firmness designations are, we needed a scale that would make sense to you, our readers.

We rate mattresses on a scale of 1 to 10, where 1 is the softest and 10 the firmest.

Our firmness scale is based on our personal experiences and comparisons with different people in different sleeping positions.

Using our scale, we would recommend the following degrees of firmness to people with different sleeping positions:

Firmness level General feel Recommended sleeping position
1 - 4 Very soft Side sleepers
5 - 7 Medium-firm Good for most sleeping positions
8 - 10 Very firm Only for stomach and back sleepers

Can I change my mattress's firmness level?

Unfortunately, this isn't really possible.

Some mattress brands offer their mattresses in different levels of firmness, so you can choose whether you want the mattress in soft, medium, or firm before you buy.

Other brands, like Emma, can provide an additional layer to add some softness or firmness to the mattress.

But, generally, it's near to impossible to change the level of firmness once you've bought a mattress.

There are still ways to fix the problem.

Risk-free trial periods

If the mattress you've just bought is too firm or too soft and you're still within the trial period, you can simply return your mattress - free of charge - and get a full refund.

But, unfortunately, if the trial period has expired, you'll have to consider buying a new mattress.

Mattress toppers

If your mattress is too firm, though, you're in luck as this can possibly be fixed by investing in a mattress topper.

Mattress toppers are great as they're generally intended to soften up a firm mattress.

Toppers can be made from a variety of materials, including memory foam, cold foam, or latex foam.

A mattress protector is something entirely different. Mattress protectors are generally thin, waterproof layers that help safeguard your mattress against dirt, spills, stains, and bacteria. They have no effect on the firmness of your mattress.

If your aim is to add a cushioning top layer to your mattress to increase its softness, we'd recommend opting for a memory foam mattress topper.

We've recommended a few of our favourite ones below.


Finding the right degree of firmness is essential, not only to the quality of your sleep but also to your health.

You need to find a mattress that will support you and keep your spine in an optimal alignment so you can wake up feeling refreshed and without any sort of tensions, aches, or lower back pain.

Our Sleep Hero firmness scale has been specifically designed to help you navigate the world of mattress firmness and find the mattress that's perfect for you.

Frequently asked questions

  • What are contour zones?

    Some mattresses consist of contour zones, which influences the overall support and stability of the mattress.

    These generally appear in the base layer of the mattress.

    A typical zoned mattress will consist of 3, 5, 7, or even 9 contour or comfort zones.

    These are usually divided into the following zones.

    Hips (pelvic area)

    This is the heaviest part of the body and the mattress must be able to provide sufficient support.

    But, it must also be soft enough so that the pelvic area can sink into the foams sufficiently if the sleeper lies on his or her side, enabling the spine to remain in a straight alignment.

    Lower back (lordosis area)

    The mattress will need to be able to provide additional firmness and support in this area to prevent the formation of a hollow back.


    This is another centre of gravity for the body.

    The mattress must provide enough support but allow for enough sinkage in the shoulder area.

    Head and feet

    The head and the feet are comparatively light parts of the body and should, therefore, lie on a relatively soft zone.

  • Which mattresses are best for your back?

    A mattress that's good for your back will offer a high degree of stability, body-contouring support, and pressure relief.

    We can highly recommend memory foam mattresses.

    These are often designed as orthopaedic mattresses.

    Many people will also benefit from a mattress with contour zones.

    Contour zones make it easier for your body to sink into the foams more deeply where required and be better supported where required. 

    A side sleeper, for example, will need to sink in more deeply in the shoulder and hip areas and require more support elsewhere. 

  • Which degree of firmness should I choose if I struggle with herniated discs?

    If you suffer from a herniated disc [2], then choosing a mattress with the right support is of enormous importance.

    It is important to immediately relieve pressure and ensure that the spine always remains in a healthy alignment.

    In order to achieve this, your mattress of choice shouldn’t be too firm or too soft.

    For most people, soft or medium-firm mattresses in the H2 or H3 range should be good.

    However, it may also be helpful to discuss this with your orthopaedist, who will be able to give you valuable tips. 

  • I’m overweight. Which degree of firmness should I choose?

    Anyone who weighs more than 100 kg (220 lbs) needs to pay special attention to the right degree of firmness.

    The incorrect firmness can lead to severe back, neck, and spine problems.

    We would recommend buying a firm mattress in the H4 range.

    If you weigh over 140 kg (308 lbs), then considering an H5 mattress would also be a good idea. 

    Overweight people will benefit from buying a barrel pocket spring mattress.

    This will ensure that the mattress adapts well to the body and provides adequate pressure relief

    Pocket sprung mattresses also have the added advantage of allowing for good airflow, which is great for heavy sweaters.

  • Does mattress size impact mattress firmness?

    No, the size of your mattress will not have an effect on the firmness of your mattress.

    You can choose your desired mattress with your preferred level of firmness in a number of different sizes.

    The standard UK mattress sizes include:

    • Small single mattresses
    • Single mattresses: 90 x 190 cm
    • Small double mattresses: 120 x 190 cm
    • Double mattresses: 135 x 190 cm
    • King-size mattresses: 150 x 200 cm
    • Super-king-size mattresses: 180 x 200 cm
    • Emperor mattresses: 200 x 200 cm

    Singles can generally choose any mattress size, while couples should opt for double mattresses or larger ones.

  • References



Editor & Certified Sleep Therapist

Nicky is an experienced writer and editor with numerous qualifications. As a certified sleep coach, her interests lie in understanding how sleep problems arise from hormonal and environmental issues, particularly as part of stress and anxiety management.

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