I’ve tested medium-firm mattresses — here’s why I don’t think they’re for everyone

Before I began my job as a Senior Sleep Writer at Tom's Guide, I'd never heard of medium-firm mattresses. But the more I learnt about their keen balance of comfort and support, the more I wanted to try one.

To me, a top-rated medium-firm mattress promises that Goldilocks level of softness; body-cradling comfort for your shoulders and hips with soothing support for your neck and spine.

That's partly why you'll find plenty of medium-firm beds in this year's guide to the best mattress, as the firmness rating is said to be ideal for most sleep positions.

So why was I let down when I got the chance to test one?

Here, I break down why the medium-firm mattresses I've tested so far haven't lived up to my lofty expectations, and why they may not live up to yours...

What is a medium-firm mattress?

Whenever I test a mattress, I (alongside a testing panel) give it a score across all key areas of performance. We score it for temperature regulation (how well a mattress regulates your temperature as you sleep), edge support (how sturdy the edges are for sitting and sleeping), and motion isolation (how well a mattress prevents movement transferring across the top of the bed.)

In addition to rating these key areas, we each also rate the mattress firmness level.

We rate a mattress's firmness level on a scale of one to 10. One is marshmallow-soft, while 10 is plank-firm. Meanwhile, a medium-firm mattress falls between 6-8 on the firmness scale — not quite soft but not quite firm.

The medium-firm mattresses I've tested...

I have been part of the testing panel for a number of medium-firm beds. The first mattress I ever tested formed part of our Helix Midnight Luxe mattress review, Luxe being a medium-firm luxury hybrid designed for side sleepers.

The Midnight Luxe shot to the top of our guide to best mattress for side sleepers on the strength of its performance, with our lead tester Nicola describing its pressure relief as "blissful." However, I personally felt it was way too firm for me, and didn't have the luxury plushness I had imagined.

Next, I became the lead tester for the Nolah Natural 11 mattress review. The brand aims to craft dream mattresses for side sleepers so, as someone who sleeps predominantly on my side, I was eager to try it.

However, despite Nolah's medium-firm rating of 6/10, the Nolah Natural was still too firm for me and didn't provide enough cushioning for my pressure points (shoulders and hips) when I slept on my side.

3 reasons why medium-firm mattresses won't be for everyone

So, why did I find the supposedly one-size-fits-all mattresses uncomfortable? Here are some reasons why not everyone will like medium-firm mattresses...

1. They're too firm for some side sleepers

If you predominantly sleep on your side, you will need a softer mattress than back and stomach sleepers, especially if you weigh under 130lbs.

Comfortable side sleeping requires enough cushioning to provide ample pressure relief in the shoulders, hips, and knees. In short, the lighter you are, the softer the cushioning you'll need.

This factor was obviously the problem for me. As a lightweight side sleeper, I need a plusher surface than some of my fellow panelists, which is why I found the medium-firm mattresses too firm.

2. They're too soft for some stomach sleepers

If side sleepers need more cushioning, then stomach sleepers need much less.

There's a good reason why most of the mattresses for stomach sleepers we recommend have a firm rating rather than medium-firm. Those who lie on their front need firmer support to keep their hips from sinking into the mattress.

Why is that important? If your hips sink into the mattress, your spine dips out of alignment which leads to lower back pain.

While front sleepers who weight under 130lbs may get enough support from a medium-firm bed, most average-weight and plus-sized stomach sleepers will need a decent firm mattress for full support.

3. Mattress firmness is subjective

Last but not least, a firmness level isn't set in stone. What may be medium-firm to some people may feel soft or firm to others.

For example, I was looking forward to being the lead tester for the Leesa Legend Hybrid mattress review, as Leesa described the mattress as medium-plush based on customer surveys.

However, to me, the Leesa Legend was much firmer than medium-plush, going to show that you can't always trust a website's firmness rating.

So what mattress type is right for me?

Medium-firm mattresses are right for lots of people, but not all — and certainly not me. When it comes to choosing the right mattress, there are several factors to take into account. Your sleeping position, weight and body type all indicate how firm your mattress should be. With that in mind, the bed I'm looking for will be a pillowy soft mattress with a firmness rating of around 4. I want a mattress that feels as plush as a marshmallow but with plenty of sink in support. What will it be? I'll let you know when I find it!