Mattress firmness guide

What do we mean by 'mattress firmness'?

Mattress firmness describes the initial sensation as you lie down: soft, medium, or firm. Support describes how well the mattress maintains the natural alignment of your spine. Tension describes the resistance built into the spring system, which responds to your body weight. These three elements work in concert. A mattress can feel soft yet support you perfectly or feel firm and still leave your spine misaligned.

Tensions are like t-shirts

Louise Silver, Product Technologist and mattress expert, often compares mattress tensions to clothing:

"Every mattress brand describes firmness differently. What one maker calls ‘medium’, another might label ‘soft’. Think of it in the same way as clothing: a size 12 t-shirt isn't a universal standard — it changes with the label, the cut, the intention of the designer. Mattress tension works in the same way; a Vispring and a Sleepeezee mattress might both say 'soft tension', but feel radically different."

How firm a mattress do you need?

You ideal firmness depends on how you sleep, your body weight, and your personal comfort preference.

1. Your primary sleep position determines where the mattress must yield and where it must hold firm. Side sleepers need cushioning at the shoulder and hip. A softer tension prevents pressure from building at these points. Back sleepers need even, continuous support along the full length of the spine, so a medium tension is usually ideal. Front sleepers need a firmer surface to prevent the hips from dropping and pulling the lower back out of alignment.
2. Anyone who's bought a mattress with a partner knows that the same mattress feels different depending on the person lying on it. This is because body weight affects how far you sink into the spring system — and therefore how the tension is experienced.
3. Lighter sleepers will find that a mattress feels firmer than its label suggests. Average builds will generally experience the tension as intended. Heavier sleepers will find a mattress yields more readily, making it feel softer without actually being 'soft' tension. These aren't flaws in the mattress, it’s simply the nature of tension. And it's why choosing a mattress by label alone can be misleading.
4. Finally, consider what makes you comfortable. Some sleepers prefer to feel cradled and enveloped. Others want a more structured, responsive surface — the sensation of resting ‘on’ the mattress rather than ‘in’ a mattress. The right firmness balances both: what your body needs, and what allows you to drift off to sleep.

5. "Don't overlook body weight. Yes, some people are sensitive about something as personal as weight, but it's essential to finding a mattress with the right tension. And if you experience sudden weight change due to a change in lifestyle, be mindful that your mattress might feel different."