How deep should a mattress be? 20, 25, 30 cm and what the depth is made of
Mattress depth has become a selling point: 25 cm, 30 cm, 35 cm, as if more were always better. Depth tells you how tall the mattress is. It tells you nothing about what the height is made of, and a cheap 30 cm mattress can be worse than a good 22 cm one. Here is how to read it.
What depth is made of
A mattress is a stack: cover, comfort layers, springs or a foam core, base. Its depth is the sum. Two 27 cm mattresses can be built completely differently:
- 1 cm cover + 5 cm memory foam + 3 cm support foam + 15 cm springs + 3 cm base = 27 cm, a good sprung mattress.
- 3 cm quilted polyester + 2 cm foam + 22 cm low-density foam block = 27 cm, a cheap foam mattress.
The first has 8 cm of comfort layer over a tall spring unit. The second has almost no comfort layer and no springs. Same depth. So the question is never "how deep" but "how deep is each layer, and what is it".
The ranges, roughly
| Depth | What it usually is | Suits |
|---|---|---|
| Under 18 cm | Thin foam or budget open coil; sofa-bed and trundle mattresses | Occasional use, pull-out beds |
| 18 to 22 cm | Entry pocket sprung, or a decent foam mattress | Students, spare rooms, singles, bunk beds |
| 23 to 27 cm | The mainstream: a full spring unit plus 5 to 8 cm of comfort layers | Most people, most beds |
| 28 to 32 cm | Deeper comfort layers, or micro-spring layers on top of the main unit | Premium hybrids, side sleepers |
| 33 cm and up | Pillow-tops, natural fillings, two spring layers | Hotel-style and traditional premium |
Beyond about 30 cm, extra depth is comfort layers and fillings, and it should show in the spec. If a 35 cm mattress does not list what fills those centimetres, it is foam.
The depth your bed needs
- Bunk beds have a maximum mattress depth marked on the frame, usually 15 to 18 cm, for the safety rail to work. Do not exceed it.
- Pull-out sofa beds with a metal action take 8 to 12 cm. A standard mattress will not fold.
- Day beds, guest beds, trundles, ottoman guest beds take a standard mattress, usually up to 25 cm; check the frame.
- Bedside cribs need the parent's mattress top within the crib's stated height range, usually with a 25 to 30 cm mattress on a standard divan working well.
- Adjustable beds need a mattress that bends: foam or micro-spring, 20 to 25 cm.
- Ottoman storage beds and low platform frames look odd with a very deep mattress and are hard to get out of with a very thin one; 25 to 30 cm looks right.
- Divans: anything.
Getting in and out
Mattress plus base is the height you sit at. A 30 cm mattress on a 35 cm divan puts the surface at 65 cm, roughly hip height for most adults, which is comfortable to sit on and stand from. A 38 cm mattress on a tall divan can reach 75 cm, which is a climb; on a low frame it is right. If getting in and out is difficult, the total height matters more than the mattress depth.
The sheets problem
Standard fitted sheets have a pocket depth of about 25 to 30 cm. A mattress deeper than that needs "deep" (30 to 35 cm) or "extra deep" (36 to 40 cm) fitted sheets, which cost more and are sold in fewer places. If you buy a 38 cm mattress, budget for new sheets and say so to anyone buying bedding for you. We put this on the Hotel Bed page because people find out the hard way.
How we specify ours
Our chapters run from 22 cm (The Uni Student and The Empty Nester: a full 13 cm spring unit with 6 cm of comfort layer, nothing wasted) to 38 cm (The Hotel Bed: twelve listed layers, extra-deep sheets required). Every page lists each layer with its depth, so the number adds up in front of you. Compare the chapters.
The short version
- Depth is a sum. Ask what each layer is.
- 22 cm well built beats 30 cm badly built.
- Check the bed: bunks and pull-out sofa beds have limits; adjustables need foam.
- Over 30 cm, buy deep sheets.
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