Mattress Comfort Calculator
Determine the most suitable mattress firmness level based on your body weight, sleeping position, comfort preference, and body support needs. This calculator follows widely accepted sleep science principles for proper spinal alignment and optimal comfort.
Mattress Comfort Results
How the Mattress Comfort Calculator Works
Mattress firmness is scored on a 1–10 scale, where 1 is a marshmallow and 10 is a board. The calculator starts everyone at 5 (medium) and adjusts for the factors sleep research says matter most:
Firmness = 5 ± position (side −1.5 / stomach +1.5) ± weight (under 60 kg −1 / over 90 kg +1.5) ± preference
Sleeping position is the biggest lever. Side sleepers need a softer surface that lets shoulders and hips sink enough to keep the spine straight; stomach sleepers need the opposite — firm support that stops the hips sagging into an arched-back position. Body weight then scales the whole equation: the same foam that cradles a 55 kg sleeper simply collapses under a 100 kg one, so heavier bodies need firmer builds to get the same effective support. Personal preference and partner-sharing nudge the final score, and the result maps to a firmness label plus the mattress types (memory foam, hybrid, latex, innerspring) that typically deliver it.
How to Choose a Mattress You'll Still Like in Year Five
Trust the trial period over the showroom. Ten minutes on a shop mattress tells you almost nothing — your body needs two to four weeks to adapt to a new surface, which is exactly why serious brands offer 100-night trials. Take them literally: sleep on it a month before judging.
Couples with different scores should average them, then lean slightly firm — a too-firm mattress can be softened with a topper, but nothing rescues a too-soft one. If your scores differ by more than 2 points, consider a split/dual-firmness mattress or two singles pushed together; both beat a decade of compromise.
Size the mattress to the sleepers and the room together: each adult needs at least 80 cm of width (queen for most couples, king if the room allows), and the bed still has to leave walking clearance — check the footprint against your bedroom with the storage space calculator if the room also works hard as storage. Replace mattresses at 7–10 years; sagging past 2–3 cm at the hips ends the discussion regardless of age.
Firmness Guide by Sleeper Profile
| Sleeper | Firmness score | Typical mattress type |
|---|---|---|
| Side sleeper, lighter build | 3–4.5 (soft) | Memory foam |
| Side sleeper, average build | 4–5.5 (medium-soft) | Memory foam / hybrid |
| Back sleeper | 5–6.5 (medium) | Hybrid |
| Stomach sleeper | 6.5–8 (firm) | Hybrid / latex |
| Over 90 kg, any position | +1 to +1.5 to the above | Hybrid / latex / innerspring |
Common Mistakes to Avoid
- Buying 'firm is good for your back' by default — research supports medium-firm for most back pain, not maximum firmness.
- Judging a mattress on a ten-minute showroom lie-down instead of a night trial.
- Ignoring weight: firmness labels assume an average body, and feel dramatically different outside it.
- Keeping a mattress past visible sagging because it 'still works'.
Frequently Asked Questions
What mattress firmness is best for side sleepers?
Side sleepers generally do best between 3 and 5.5 out of 10 — soft enough for the shoulder and hip to sink in and keep the spine level. Lighter side sleepers should sit at the lower end; heavier ones need the extra support of the upper end or a zoned hybrid.
What firmness is best for back pain?
The best-supported answer from clinical research is medium-firm — roughly 5.5 to 7 on the scale — not the rock-hard mattress folk wisdom prescribes. It maintains the spine's natural curve without pressure points. If pain is new or worsening, see a professional before blaming the mattress.
Do heavier people need firmer mattresses?
Yes. Above roughly 90 kg, softer foams compress fully and stop supporting, so the same comfort requires a firmer build — typically one to one-and-a-half points higher on the scale, and construction matters too: hybrids and latex hold their firmness under load far better than budget all-foam.
How often should you replace a mattress?
Every 7–10 years for most quality mattresses — latex lasts longer, budget foam less. Replace sooner if you can see body impressions deeper than 2–3 cm, wake with new aches that fade during the day, or sleep noticeably better in hotel beds than your own.