Mattress Firmness Guide: Soft, Medium or Firm?

Quick Answer: This mattress firmness guide explains why there is no single right firmness for everyone, as the best choice depends on your sleeping position, body weight, build and personal comfort preferences.

Choosing a new mattress involves more than deciding what size you need or how much you want to spend. One of the biggest considerations is firmness, particularly when you're trying to work out whether a soft, medium or firm mattress will give you a comfortable night's sleep.

The difficulty is that firmness can be surprisingly subjective. A mattress that feels perfectly comfortable to one person might feel too soft or too hard to someone else. Even firmness ratings aren't always straightforward, as manufacturers can use different scales to describe their products.

Understanding what firmness actually means, and how it differs from support, can make choosing your next mattress considerably easier.

What Does Mattress Firmness Mean?

Mattress firmness describes how soft or hard a mattress feels when you lie on it. Essentially, it's the level of resistance you experience as your body presses into the sleeping surface.

A softer mattress generally allows more noticeable sinking, whereas a firmer mattress tends to resist that pressure and creates a more solid sleeping sensation.

However, firmness isn't necessarily the same as comfort. Some people enjoy the cushioning feeling of a softer mattress, while others prefer sleeping on a surface that feels more substantial.

Mattress materials, construction and comfort layers can all influence how firm a mattress feels. This is why two mattresses described as medium may still offer noticeably different sleeping experiences.

Firmness vs Support: What Is the Difference?

Although firmness and support are often discussed together, they're not interchangeable.

Firmness refers to how a mattress feels against your body. Support describes how effectively the mattress helps maintain your body's position, including the natural alignment of your spine.

A firm mattress isn't automatically more supportive than a softer alternative. Equally, a softer mattress can provide suitable support when its construction responds appropriately to your body.

For example, a mattress might have a cushioned surface that allows your shoulders and hips to settle comfortably, while the underlying layers provide the resistance needed to prevent excessive sinking.

When choosing a mattress, it's worth considering both characteristics rather than assuming that greater firmness always means better support.

The Firmness Scale Explained

Mattress firmness is commonly described using a numerical scale, often running from 1 to 10. However, there's an important detail that can make these ratings confusing.

Not every manufacturer or testing organisation uses the scale in the same direction.

Some mattress brands use 1 to represent the softest feel and 10 to represent the firmest. Other testing methods reverse this arrangement.

For example, the independent testing used for True Rest follows a scale where:

• 1 represents firm

• 10 represents soft

This means a higher number indicates a softer feel within that particular testing system.

Before interpreting any mattress firmness rating, always check which direction the scale runs. A rating of 6 on one scale cannot automatically be compared with a rating of 6 from another manufacturer.

The testing method and definitions matter just as much as the number itself.

Soft, Medium and Firm Mattresses Compared

Understanding the general differences between firmness categories can help you narrow down your options.

These descriptions are general guidelines rather than fixed rules. Your preferred firmness will depend on several factors, including how you sleep and how your weight is distributed across the mattress.

Remember that mattresses in the same firmness category can feel different because of their materials and internal construction.

How Sleeping Position Affects Firmness Preference

Your usual sleeping position can influence which firmness feels most comfortable, since different positions put pressure on different parts of your body.

Side Sleepers

Side sleepers typically place more concentrated pressure on their shoulders and hips.

A mattress with some cushioning may let these areas settle comfortably while helping maintain a natural spinal position.

If a mattress feels excessively firm, some side sleepers may experience uncomfortable pressure around their shoulders or hips. However, a mattress that's too soft may allow the body to sink unevenly.

Medium or softer-feeling mattresses may appeal to some side sleepers, depending on their build and individual preferences.

Back Sleepers

Back sleepers generally benefit from a mattress that supports the body's natural curves without letting the hips sink too much.

A medium feel may offer a comfortable balance for many back sleepers, though preferences vary widely.

The important consideration is whether the mattress feels supportive across the shoulders, lower back and hips.

A mattress that feels comfortable when you first lie down should also provide a consistent sleeping surface throughout the night.

Front Sleepers

Front sleepers often prefer a surface that limits excessive sinking around the hips and abdomen.

If the middle of your body sinks too far into the mattress, it may put your lower back in an uncomfortable position.

For this reason, some front sleepers prefer a firmer sleeping surface. However, that doesn't mean the firmest available mattress is necessarily the most comfortable.

Body weight, mattress construction and individual preferences should still influence the decision.

How Body Weight and Build Affect Firmness

Body weight and build can influence how a mattress responds when you lie on it.

Someone with a lighter build may compress the comfort layers less than someone with a heavier build. As a result, the same mattress may feel relatively firm to one person and noticeably softer to another.

Weight distribution also matters. People with broader shoulders or hips may experience pressure differently from those with a more evenly distributed build.

This doesn't mean particular body types must use specific firmness levels. Instead, it highlights why you should consider mattress firmness alongside individual comfort and sleeping position.

When testing a mattress, pay attention to how your shoulders, hips and lower back feel rather than choosing a firmness based solely on your weight.

Do Mattresses Soften Over Time?

Mattresses can change in feel as you use them, but the extent of these changes depends on their materials, construction, and overall quality.

During the initial settling-in period, comfort layers may begin to respond differently as the mattress adjusts to regular use. You may also become more accustomed to the feel of your new sleeping surface.

Over longer periods, repeated pressure can contribute to changes in cushioning and firmness. However, the rate and extent of these changes vary between products.

Some gradual changes are normal, but significant sagging or noticeable loss of support may indicate wear.

Following the manufacturer's care instructions, including any guidance about rotating the mattress, can help you look after it properly.

How to Check a Firmness Claim

When comparing mattresses, it's useful to look beyond descriptions such as soft, medium or firm.

Start by checking whether the manufacturer explains how its firmness rating was determined.

If a numerical scale is provided, establish which end represents firm and which represents soft. Without this information, the number offers limited practical value.

Independent testing can provide additional context because it uses defined procedures to assess mattress characteristics.

You should also consider the opportunity to experience the mattress yourself. Even independently tested firmness ratings cannot guarantee how comfortable a particular mattress will feel to you.

A home trial can be especially useful because it allows you to experience the mattress across multiple nights rather than relying on a brief showroom test.

Before purchasing, check the manufacturer's returns policy for the applicable conditions, settling-in requirements and return arrangements.

Where True Rest Sits on the Scale

A True Rest mattresses was tested by FIRA International to BS EN 1957, providing a defined basis for assessing firmness.

True Rest is rated medium, with a firmness rating of 6 out of 10 on a scale where 1 represents firm and 10 represents soft.

This rating describes the mattress within the particular testing system used. It shouldn't be directly compared with ratings from brands using different scales or assessment methods.

A medium mattress is designed to offer a balance between cushioning and resistance, although the experience will naturally vary depending on the individual.

For anyone considering a new mattress, understanding the confirmed rating can help establish what to expect before making a purchase.

You can explore the True Rest mattress range for further information about the available products, construction and comfort features.

Conclusion

Choosing the right mattress firmness is ultimately about finding a sleeping surface that feels comfortable and provides suitable support for your body.

While sleeping position, weight, and build can guide your decision, no single firmness level works for everyone.

Understanding the difference between firmness and support, checking how ratings are measured and taking advantage of a home trial can all help you make a more informed choice.

With True Rest's independently tested medium firmness rating, you also have a clear reference point when considering whether its mattresses suit your preferences.

Frequently Asked Questions (FAQs)

What firmness is best for most people?

There isn't one firmness that's best for everyone. Medium mattresses may appeal to a wide range of sleepers because they balance cushioning and support. However, sleeping position, body weight and personal preference all influence comfort. The most suitable option is one that feels comfortable while providing appropriate support.

Is a firm mattress better for your back?

Not necessarily. A firmer mattress isn't automatically better for back comfort, as the right level of support depends on your body and sleeping position. Some people may prefer a firmer surface, while others find a medium or softer mattress more comfortable. Our guide to choosing a mattress for back pain explores the considerations in more detail.

What does medium firm mean?

Medium firm is a general mattress description used for a feel somewhere between medium and firm. It typically suggests noticeable support with some surface cushioning. However, manufacturers may interpret the term differently, so check their firmness definitions and rating systems. True Rest describes its mattress as medium.

Should a mattress be firm or soft?

A mattress should feel comfortable while supporting your body appropriately. Softer mattresses may offer more cushioning around pressure points, while firmer mattresses generally resist sinking more. Neither is automatically better. Your sleeping position, build, and personal preferences should guide your choice.

How long does it take to get used to a new mattress?

Adjusting to a new mattress can take time, particularly if its firmness or construction differs from your previous one. True Rest offers a 30-night settling-in period, giving your body time to adjust to the new sleeping surface. Check the True Rest returns information for the full terms and conditions.