The mattress firmness scale runs from 1 to 10, where 1 is the softest and 10 is the firmest. Most beds sit between 3 and 9. In short: side sleepers tend to do best around 3 to 5, back sleepers around 5 to 7, stomach sleepers around 6 to 8, and heavier sleepers usually need one step firmer than those numbers.
This guide is only about feel. If you are still choosing between coils and all foam, read our hybrid vs memory foam mattress guide first, since any construction can be built soft or firm.
The mattress firmness scale explained
Firmness describes how much a mattress gives under your weight. A soft bed lets you sink in; a firm bed keeps you near the surface. There is no industry standard, so labels vary by brand. The Sleep Foundation rates beds on its own 10 point scale and notes that everyone perceives firmness differently, and that a true 10 is rare and would feel uncomfortable to most sleepers. The table follows Sleep Foundation labels, with feel notes in line with Castlery’s mattress firmness guide.
| Scale | Label | Feel | Who it tends to suit |
|---|---|---|---|
| 1 to 3 | Soft, plush, ultra plush | Deep cushioning, noticeable sink, hugs the body | Lightweight sleepers and side sleepers who want pressure relief at the shoulders and hips |
| 4 | Medium soft | Soft top with a bit more support underneath | Side sleepers and lighter sleepers who want contouring without sinking too far |
| 5 | Medium | Balanced contouring and support | Combination sleepers and average weight sleepers |
| 6 | Medium firm | Light cushioning, little sink | Back sleepers, couples and many average weight adults |
| 7 to 8 | Firm | Minimal sink, you sleep “on” the bed | Stomach sleepers, back sleepers and heavier sleepers |
| 9 | Extra firm | Very little give, strong pushback | Heavier back and stomach sleepers |
| 10 | Rarely made | Close to no give | Very few people |
One point Castlery makes well: firmness and support are not the same thing. Support comes from the core and keeps your spine in line; firmness comes from the comfort layers and is how the bed feels.
Best firmness by sleep position
Treat these as general starting points. Comfort is personal.
Best firmness for side sleepers
Your shoulder and hip carry most of your weight, so a bed that is too firm pushes back at those points. Castlery suggests soft to medium (3 to 5) for most side sleepers. Waking with a sore shoulder or numb arm can mean the bed is too firm. Heavier side sleepers often do better a step firmer: the Sleep Foundation’s chart puts side sleepers over 230 pounds at medium firm (6) to firm (7).
Back sleepers
You want cushion for the curve of your lower back without letting the hips sink. Medium to medium firm (5 to 7) is the usual range.
Stomach sleepers
A soft bed lets the hips sink and the lower back arch. Medium firm to firm (6 to 8) is the common recommendation.
Combination sleepers
If you move around, medium to medium firm (5 to 7) lets you turn without feeling stuck.
How body weight changes the feel
The same mattress feels firmer to a lighter person and softer to a heavier one. The Sleep Foundation publishes these ranges:
| Body weight | Side sleepers | Back sleepers | Stomach sleepers |
|---|---|---|---|
| Under 130 lbs | Soft (3) to Medium (5) | Soft (3) to Medium (5) | Medium Soft (4) to Medium Firm (6) |
| 130 to 230 lbs | Medium Soft (4) to Medium (5) | Medium (5) to Firm (7) | Medium (5) to Firm (7) |
| Over 230 lbs | Medium Firm (6) to Firm (7) | Firm (7, 8) to Extra Firm (9) | Firm (7, 8) to Extra Firm (9) |
For couples, Castlery suggests medium firm as a compromise.
Medium vs firm mattress: how to choose
A medium mattress (around 5) gives more contouring and pressure relief and works for the most positions. A firm mattress (around 7 or 8) keeps you higher on the surface and limits hip sink.
- Pick medium if you sleep on your side or switch positions, weigh under about 230 pounds, or wake with shoulder or hip pressure.
- Pick firm if you sleep mostly on your back or stomach, weigh more than about 230 pounds, or feel “stuck” in softer beds.
A note on back pain: it is common to assume firmer is better, but Castlery points out that many people do better on a supportive medium firm bed than an extra firm one, and the Sleep Foundation stresses that individual needs vary. If you have back pain, a joint condition or another medical issue, ask your doctor or physical therapist before choosing based on firmness.
Firmness labels on the mattresses we carry
Our current mattress lineup comes from HomeRoots. Their listings use labels (ultra plush, plush, medium, firm, extra firm) rather than numbers, so the scale positions below are our rough mapping, not a manufacturer rating.
| Mattress | Listed comfort | Listing says | Price |
|---|---|---|---|
| 15″ Copper Infused Cal King Ultra Plush Hybrid | Ultra plush (soft end) | Cradles the body closely; suited to lightweight bodies | $1,269.99 |
| 11″ Cal King Foam Plush Euro Top Hybrid | Plush | Ideal for side sleepers, eases pressure on shoulders and hips | $899.99 |
| 10″ Cal King Foam Medium Hybrid | Medium | Not too plush or too firm; works for all sleep positions | $859.99 |
| 10″ Queen Foam Medium Hybrid | Medium | Designed for a variety of sleep positions | $264.99 |
| 10″ Cal King Foam Firm Hybrid | Firm | Firm comfort level over pocket coils | $864.99 |
| 13″ Copper Infused Cal King Firm Hybrid | Firm | A great choice for back sleepers, keeps hips aligned | $1,139.99 |
| 11″ Cal King Foam Extra Firm Hybrid | Extra firm | Ideal for stomach sleepers or a heavier build | $959.99 |
| 13″ Copper Infused Cal King Extra Firm Hybrid | Extra firm | Extra firm comfort for a sturdier surface | $1,059.99 |
All of these ship compressed in a box, and several listings say a box spring is not needed. A thicker mattress also raises your total bed height, which our bed height guide covers.
How to adjust firmness after you buy
- Give it time. Castlery notes that most mattresses soften slightly as the comfort layers break in. Give a new bed a few weeks.
- Add a topper to soften. A foam or fiber topper is the easiest way to make a firm bed feel softer on top. It cannot fix a sagging mattress.
- Check the foundation. A sagging or widely slatted base makes any mattress feel softer and less even. See platform bed vs box spring for what each mattress type needs.
What to expect from trials and returns
Some mattress brands offer long home trials, often with a break in period. Those terms belong to each seller, so do not assume they apply everywhere. Before you order from us, read our return and refund policy and call us with any questions about a specific mattress.
Frequently asked questions
What number is medium firm on the mattress firmness scale?
Medium firm is usually a 6, with medium at 5 and firm at 7 or 8. Brands rate their own beds, so numbers are approximate.
What is the best firmness for side sleepers?
Most side sleepers do well between soft and medium (3 to 5). Side sleepers over about 230 pounds often need medium firm (6) to firm (7) so their hips do not sink too far.
Is a medium vs firm mattress better for couples?
Medium firm is the usual middle ground for couples, since it works for back, side and combination sleepers of average weight.
Is a firm mattress better for back pain?
Not necessarily. Alignment matters more than firmness, and many people find a supportive medium firm bed more comfortable than an extra firm one. Ask your doctor if you have ongoing pain.
Have a question about a mattress or which firmness to pick? Call us at 866-777-2590, Monday to Friday, 9AM to 6PM PST. Shipping is free freight on orders of $999 or more, and a flat $200 below that. For bedroom furniture beyond the mattress, start with our guide to buying designer furniture online.
