Prices shown are approximate. Verify current pricing before purchasing.
Mattress firmness is described on a 1-10 scale where 1 is the softest possible and 10 is the firmest. Almost no mattresses sit at the extremes — the practical range is 3-9. Picking the right firmness for your sleep position and body weight is the single most important mattress decision you make.
The firmness scale explained
- 1-2: Extra soft. Almost all sink. Rare commercial offering.
- 3-4: Soft / Plush. Deep contouring. Side sleepers and lighter weights.
- 5: Medium-soft. Most contouring without significant sink.
- 6: Medium. Balanced. Works for most combination sleepers.
- 7: Medium-firm. Most popular firmness. Back sleepers, average couples.
- 8: Firm. Stomach sleepers, heavier sleepers, traditional bed feel.
- 9-10: Extra firm. Specialty use. Hospital-style, post-surgery recovery.
Firmness by sleep position
Side sleepers
Need: 4-6 (medium-soft to medium). The shoulder and hip must sink in for spinal alignment.
Symptom of wrong firmness: Shoulder pain, hip pain, numb arm/hand on the down side.
Back sleepers
Need: 5.5-7 (medium-firm). Lumbar must be supported without hammock effect.
Symptom of wrong firmness: Lower back pain, morning stiffness in the lumbar.
Stomach sleepers
Need: 7-8.5 (firm). Hips must not sink at all.
Symptom of wrong firmness: Lower back pain from lumbar arching, neck strain from twisted head.
Combination sleepers
Need: 6-7 (medium-firm). The compromise firmness that handles all positions reasonably.
Firmness by body weight
Body weight changes how a mattress feels. The same mattress feels softer to a heavier sleeper and firmer to a lighter sleeper because heavier weight compresses the comfort layer more deeply.
- Petite (under 130 lbs): Add 1 to the recommended firmness (a “medium-firm” 7 will feel like 8 to you). Pick mattresses 1 step softer than the standard recommendation.
- Average (130-230 lbs): Standard recommendations apply.
- Heavier (230+ lbs): Subtract 1 from the recommended firmness. A “medium-firm” 7 will feel like 6. Pick mattresses 1 step firmer than the standard recommendation.
How to test firmness without a showroom
If you cannot test in person, three approaches:
1. Use the trial period
The 100-365 night trial is exactly for testing firmness in your actual bedroom. Sleep on the new mattress for 30 nights. If it is wrong, return it.
2. Check independent reviewer firmness ratings
Brand-stated firmness ratings are sometimes optimistic (“medium” when it is really firm). Independent reviewers test with consistent methodology. Cross-reference 2-3 sources.
3. Match to your current mattress
If your current mattress works for you, find the firmness rating of the model and pick a new one with similar rating.
Common firmness mistakes
Buying “firm” because you think firm is supportive
Firm and supportive are not the same. A medium-firm mattress with proper construction supports your spine better than a firm mattress without zoned support. Side sleepers especially: firm is wrong.
Buying soft because the showroom version felt good for 5 minutes
Showroom comfort does not predict 8-hour sleep comfort. A soft mattress that feels relaxing for a brief test causes back pain at hour 4.
Buying medium-firm “because everyone recommends it”
Medium-firm is the most common recommendation but it is wrong for some shoppers. Side sleepers under 150 lbs need softer; stomach sleepers need firmer. Match to your specific situation.
Buying without considering body weight
Two sleepers of identical sleep position but different weight need different firmness. The brand’s stated firmness is calibrated for an average-weight sleeper.
Firmness and motion isolation
Firmer mattresses transfer motion more than softer mattresses. If you share the bed with a restless partner, prioritize motion isolation (memory foam) over edge support (firmer hybrids). The firmness compromise might mean choosing a softer-than-ideal mattress to get better motion isolation.
Firmness and edge support
Firmer mattresses have better edge support. If you sit on the bed regularly, sleep near the edge, or share with a partner, edge support matters. Pure-foam soft mattresses (like soft Nectar) have weak edges; firm hybrids (like Saatva Firm) have excellent edges.
Should you flip your mattress?
Most modern mattresses are one-sided and cannot be flipped. The construction has the comfort layer on top and the support core on the bottom; flipping makes them sleep wrong. Confirm the brand instructions before flipping.
Two-sided flippable mattresses (Brooklyn Bedding Plank, Sweetnight Twilight) have two distinct firmness sides. Flip when you want to try the other.
How to pick today
Identify your sleep position, identify your body weight, look up the recommended firmness above, then pick a mattress with that firmness rating from the shortlist. The hardest part of mattress shopping is firmness selection. Get this right and the brand decision becomes much easier.
Reminder: Confirm current pricing before purchase.