Reference

Standard shelf dimensions: a practical reference

The short version: for most home shelving, aim for 25–30 cm depth and 20–30 cm of vertical space between shelves. Span is not one number: in 18 mm MDF, 30 cm deep, the builder adds a center support from 48 cm of width for everyday use, and from 40 cm for a heavy load. A thicker board or a stiffer material goes further before it needs one. Here are the details.

Shelf depth (front to back)

Depth depends on what you store.

Use	Typical depth
Paperbacks, small items	18–22 cm
General books, most shelving	25–30 cm
Binders, large books, display	30–40 cm

A depth of 28–30 cm suits most general-purpose shelving.

Vertical spacing (gap between shelves)

Leave a little headroom above the tallest item.

Contents	Spacing
Paperbacks	~20 cm
Hardbacks, larger books	~28–30 cm
Display, decor, baskets	35 cm and up

Shelf span (width between supports)

This is where most shelves fail: too wide, and the shelf sags over time. For 18 mm MDF, a common DIY material, 30 cm deep, here is how many supports the builder adds:

Figures for France, where 18 mm MDF is on sale. Your country may stock different boards, and the builder tells you which spans yours allow.

Shelf width	Medium load	Heavy load
40–47 cm	No support	One center support
48–74 cm	One center support	One center support
75–94 cm	One center support	2 supports
95–111 cm	2 supports	2 supports
112–141 cm	2 supports	3 supports
142–148 cm	3 supports	3 supports
149–185 cm	3 supports	4 supports
186–188 cm	3 supports	5 supports
189–222 cm	4 supports	5 supports
223–235 cm	4 supports	6 supports
236–259 cm	5 supports	6 supports
260–280 cm	5 supports	7 supports
Over 280 cm	This width needs panels larger than the biggest standard board	This width needs panels larger than the biggest standard board

In short: in 18 mm MDF, 30 cm deep, the builder adds a center support from 48 cm of width for everyday use, and from 40 cm for a heavy load. A thicker board or a stiffer material like pine goes further before it needs one.

Shelf thickness

12 mm: light loads, short spans only.
18 mm: the standard for most home shelving.
25 mm or pine: long spans or heavy loads (books, records, tools).

Height and safety

Tall units tip over, especially with children around. Anti-tip brackets (small L-shaped parts) are listed in every plan for a storage unit, a wardrobe or an under-slope unit, whatever the height: from 68.6 cm, above a height of 4.5 times the depth, or in a child's room, fixing to the wall is required, not just recommended. Fix into a stud, one of the bars hidden behind the board, or into a solid wall if you can; otherwise, see the guide “Fixing furniture to the wall”.

How Kamba uses these rules

Kamba applies these limits to your exact dimensions automatically. When you enter a width, depth, material, and expected load, it checks the span against the limits above, adds a center support when needed, flags when a stronger material is required, and includes the anti-tip hardware. You get a plan calculated for your measurements, not a guess.