How to Choose Mattress Firmness by Sleep Position
The right firmness keeps your spine aligned and pressure points cushioned. Your ideal firmness depends on how you sleep and your body weight.
The Quick Answer
80% of sleepers prefer a firmness between 5-7 on a 10-point scale. The most popular rating is 6 (medium-firm), which offers a good balance of comfort and support for most people.
Firmness vs Support: What's the Difference?
Many people confuse firmness with support, but they're different things:
Firmness
How soft or hard the mattress feels when you first lie down. This is the initial sensation – how much you sink in and how the surface conforms to your body.
Support
How well the mattress keeps your spine aligned throughout the night. A mattress can be soft yet supportive, or firm yet lacking proper support.
💡 Key insight: You need both the right firmness AND proper support. A mattress that feels comfortable but doesn't support your spine properly will lead to back pain over time.
The Mattress Firmness Scale Explained
Most mattress reviews use a 1-10 firmness scale. In practice, almost all mattresses fall between 3-9, as extremes are uncomfortable for most people.
| Rating | Feel | Description | Best Suited For |
|---|---|---|---|
| 1-2 | Extra Soft | Very deep sinkage, maximum conforming | Rarely recommended – insufficient support for most |
| 3 | Soft | Significant sinkage, close body hugging | Very lightweight side sleepers (<55kg) |
| 4 | Medium Soft | Noticeable sinkage, good pressure relief | Lightweight sleepers, side sleepers under 75kg |
| 5 | Medium | Balanced sinkage and support | Average weight side sleepers, lighter back sleepers |
| 6 | Medium Firm | Slight sinkage, moderate conforming | Most popular – suits majority of sleepers |
| 7 | Slightly Firm | Minimal sinkage, good support | Back/stomach sleepers, heavier side sleepers |
| 8 | Firm | Very little sinkage, strong support | Heavier sleepers (100kg+), stomach sleepers |
| 9-10 | Extra Firm | Almost no give, maximum support | Very heavy sleepers, specific medical needs |
Visual Firmness Scale
Firmness by Sleep Position
Your sleep position is the most important factor in choosing firmness. Here's what experts recommend:
🛏️Side Sleeper
Side sleeping puts pressure on shoulders and hips. A softer mattress allows these areas to sink in, keeping the spine aligned.
🔙Back Sleeper
Back sleepers need lumbar support to prevent the lower back from sinking. A firmer surface maintains proper spinal curvature.
⬇️Stomach Sleeper
Stomach sleeping can strain the lower back. A firmer mattress prevents the pelvis from sinking too deep, reducing spinal stress.
🔄Combination Sleeper
Combination sleepers need versatility. A medium-firm mattress offers enough support and comfort across all positions.
How Body Weight Affects Firmness
The same mattress feels different depending on your weight. A 60kg person and a 100kg person will experience different levels of sinkage and support on identical mattresses.
Lightweight
Under 60kg (9.5 stone)Lighter sleepers don't compress mattress materials as much, so a softer mattress feels firmer to them. They typically need softer options (3-5) for adequate pressure relief.
Average Weight
60-100kg (9.5-15.5 stone)Most mattresses are designed for this weight range. Medium to medium firm (5-7) works well for most sleepers in this category.
Heavyweight
Over 100kg (15.5+ stone)Heavier sleepers compress materials more deeply and need firmer support (6-9) to maintain proper alignment and prevent bottoming out.
Signs Your Mattress Firmness is Wrong
Too Soft
- •Waking up with lower back pain
- •Feeling like you're sinking into a hammock
- •Difficulty changing positions during sleep
- •Hips sinking deeper than shoulders
- •Feeling unsupported or unstable
Too Firm
- •Pressure pain in shoulders or hips (side sleepers)
- •Numbness or tingling in arms/hands
- •Tossing and turning to get comfortable
- •Gaps between your body and the mattress
- •Waking up with stiff, achy joints
Special Considerations
Couples with Different Preferences
If partners prefer different firmness levels, consider:
- • Split firmness mattresses – different firmness on each side
- • Medium-firm compromise – works for most combinations
- • Mattress toppers – add softness to one side if needed
Back Pain Sufferers
Research shows medium-firm mattresses (5-7) are often best for back pain:
- • Provides support without creating pressure points
- • Maintains natural spinal curvature
- • Allows some conforming for comfort
- • Consult a physiotherapist for personalised advice