Firm vs Medium vs Soft Mattress: How to Choose the Right Firmness

Why Firmness Matters More Than Brand

What actually determines whether you wake up refreshed or sore is firmness relative to your body. A mattress rated medium-firm by the manufacturer might feel firm to a 55kg person and soft to a 100kg person.

The Firmness Scale Explained

Soft (1-3): Deep sinking, maximum contouring. Best for lightweight side sleepers under 65kg.

Medium-soft (4-5): Noticeable contouring with some support beneath. Good for average-weight side sleepers.

Medium-firm (5-7): The most universally comfortable range. Suits most body types and sleep positions.

Firm (7-8): Minimal sinking. Strong pushback. Best for back sleepers, stomach sleepers, and heavier individuals over 90kg.

Extra-firm (9-10): Very little give. Rarely recommended unless specifically preferred.

Matching Firmness to Sleep Position

Side sleepers need softer surfaces (4-6) because the shoulder and hip protrude further.

Back sleepers need medium-firm (5-7) to support the lumbar curve.

Stomach sleepers need firmer surfaces (6-8) to prevent the pelvis from sinking.

Combination sleepers need medium (5-6) for versatility across all positions.

Body Weight and Firmness

Under 65kg: Choose one firmness level softer than the general recommendation.

65-90kg: Standard firmness recommendations apply.

Over 90kg: Choose one firmness level firmer. Also look for thicker support layers.

The Firmness Mistake

The most common mistake is buying too firm. Research consistently shows medium-firm outperforms firm for pain relief and sleep quality across most body types.

How Claire Handles Firmness

When you tell Claire your sleep position, body type, and any pain points, she maps these to an ideal firmness range and scores every mattress in the DOME index against that range.

This content is educational only and not medical advice.