Choosing a Mattress for Your Sleep Position

When you stand upright, your spine has a natural S-shaped curve. The goal of a good mattress is to maintain this neutral spinal alignment while you sleep, regardless of your position.

What Happens With Poor Alignment

If your mattress is too firm, your body cannot sink in enough, creating pressure points at the shoulders and hips (the widest parts of your body). If it is too soft, your body sinks too far, causing your spine to curve unnaturally.

Research published in The Lancet found that both extremes - too firm and too soft - increase morning back pain. The optimal mattress keeps your spine in its natural position throughout the night.

Pressure Points

Your body's weight is not distributed evenly when lying down. The three main pressure zones are:

• Shoulders - need to sink into the mattress (especially for side sleepers)
• Lumbar (lower back) - needs support to prevent sagging
• Hips - need a balance of cushioning and support

The right mattress provides enough give at the shoulders and hips to prevent pressure build-up, while providing enough support at the waist to keep the spine aligned.

Key Fact: A good mattress maintains your spine's natural S-curve during sleep. It must balance cushioning at pressure points (shoulders, hips) with support at the waist.

Research from the British Sleep Society suggests that approximately 69% of UK adults are primarily side sleepers, 17% back sleepers, 7% front sleepers, and 7% combination sleepers who regularly switch positions.

Side Sleepers (69%)

Side sleeping is the most common position and generally the healthiest for most adults. However, it creates the widest gap between the mattress surface and the body (at the waist), meaning the mattress needs to be soft enough for shoulders and hips to sink in while supporting the waist.

Key needs: Pressure relief at shoulders and hips, support at the waist, a pillow thick enough to keep the neck aligned with the spine.

Back Sleepers (17%)

Back sleeping distributes weight most evenly across the mattress. The main risk is the lower back arching away from the mattress surface, creating a gap that leads to lumbar pain.

Key needs: Firm enough to prevent excessive sinking, contouring at the lumbar area, moderate pillow height to keep the head neutral (not pushed forward).

Front Sleepers (7%)

Front sleeping is generally discouraged by physiotherapists because it forces the neck into rotation and can hyperextend the lower back. However, some people simply cannot sleep any other way.

Key needs: A firmer surface to prevent the pelvis sinking and hyperextending the spine, a very thin or flat pillow (or no pillow), breathable surface materials since the face is pressed into the mattress.

Combination Sleepers (7%)

Combination sleepers need a mattress that works across multiple positions - typically medium firmness with responsive materials that adapt quickly when you change position. Memory foam can feel restrictive for combination sleepers because of its slow response time; pocket springs or latex tend to work better.

Key Fact: 69% of UK adults are side sleepers. Each position has different support needs - there is no single firmness that works for everyone.

Mattress firmness is subjective - what one person calls medium, another might call firm. However, the industry uses a broadly agreed scale to help standardise descriptions.

How Firmness Is Rated

Most UK retailers and review sites use a 1-10 scale (or equivalent descriptive terms):

• 1-2 (Extra Soft): Very rare. Feels like sinking into a cloud. Too soft for most adults.
• 3-4 (Soft): Significant sinking and contouring. Good for lightweight side sleepers.
• 4-5 (Medium-Soft): Noticeable contouring with some support. Popular for side sleepers.
• 5-6 (Medium): The most popular firmness range. Balances cushioning and support. Suits most back sleepers and many side sleepers.
• 6-7 (Medium-Firm): Supportive with moderate contouring. Good for back sleepers and heavier individuals. The Lancet research found this range best for back pain.
• 7-8 (Firm): Minimal sinking. Good for front sleepers and heavier individuals.
• 9-10 (Extra Firm): Very rigid. Rarely recommended except for specific medical needs.

Body Weight Matters

Your body weight significantly affects how a mattress feels:

• Under 60kg: A mattress will feel firmer than rated. Consider going one step softer.
• 60-100kg: Mattresses will generally feel as described.
• Over 100kg: A mattress will feel softer than rated. Consider going one step firmer, and look for higher spring counts or denser foams for durability.

Key Fact: Firmness is subjective and affected by body weight. Medium-firm (5-7 on the scale) suits the widest range of sleepers. Always consider your weight alongside the firmness rating.

Here are evidence-based firmness recommendations by sleep position, taking body weight into account.

Side Sleepers: Soft to Medium (3-6)

Side sleepers need their shoulders and hips to sink into the mattress to maintain spinal alignment. If the mattress is too firm, pressure builds at these points, causing numbness, tingling, and tossing and turning.

Recommended:

• Under 60kg: Soft to medium-soft (3-5)
• 60-100kg: Medium-soft to medium (4-6)
• Over 100kg: Medium (5-6) with good-quality pocket springs

Best materials: Memory foam or latex comfort layers with pocket springs. These provide the pressure relief side sleepers need.

Back Sleepers: Medium to Medium-Firm (5-7)

Back sleepers need even support across the whole body with extra contouring at the lumbar curve. A mattress that is too soft allows the pelvis to sink, straining the lower back.

Recommended:

• Under 60kg: Medium (5-6)
• 60-100kg: Medium to medium-firm (5-7)
• Over 100kg: Medium-firm to firm (6-8)

Best materials: Zoned pocket springs with targeted lumbar support, or hybrid mattresses with responsive foam layers.

Front Sleepers: Medium-Firm to Firm (6-8)

Front sleepers need a firmer surface to prevent the pelvis from sinking and hyperextending the lower back. A very thin or flat pillow is essential to avoid neck strain.

Recommended:

• Under 60kg: Medium-firm (6-7)
• 60-100kg: Medium-firm to firm (6-8)
• Over 100kg: Firm (7-8)

Best materials: Firm pocket springs with minimal foam topping, or high-density foam.

Combination Sleepers: Medium (5-6)

Medium firmness with responsive materials (pocket springs, latex) that allow easy position changes. Avoid thick memory foam which can make rolling over difficult.

Try our Pillow Height Calculator to find the right pillow for your position.

Key Fact: Side sleepers need softer; back sleepers medium-firm; front sleepers firm. Body weight shifts the ideal firmness by 1-2 points on the scale.