What Thickness Glass for Shelves?
The question people ask is “what thickness for a shelf”. The question that actually decides it is “how far between the supports”.
Span, not length
A 1200mm shelf supported at both ends and once in the middle behaves like two 600mm shelves. The same 1200mm shelf held only at the ends is a very different problem.
Glass does not sag permanently the way timber does — it deflects under load and returns. But visible deflection looks alarming, and a shelf loaded past its limit fails suddenly rather than gradually.
A starting point
For domestic shelving with supports at both ends and a moderate load — books, glassware, ornaments:
- Up to 400mm span — 6mm is comfortable
- 400 to 700mm — 8mm
- 700 to 900mm — 10mm
- 900mm and beyond — 12mm, and consider an intermediate support
Treat these as a sensible default rather than an engineering calculation. Depth, load and support type all shift them.
What pushes you thicker
- Heavy or concentrated loads — a row of hardbacks is far heavier than it looks. So is a stack of plates.
- Deep shelves — a 400mm deep shelf carries more than a 200mm one over the same span.
- Point supports — small pin or peg supports concentrate stress at four spots. Continuous rails or channels spread it and are more forgiving.
- Cantilevered shelves — supported on one edge only. These need to be thicker and ideally engineered rather than guessed.
Toughened or not
Not required by the standard for a normal shelf inside a cabinet. Worth it anyway in two cases:
Where people are underneath. A kitchen or bathroom shelf over a bench, or anything at head height in a child’s room. Ordinary glass fails into shards.
Where the load is uncertain. Toughening buys a real margin for the times somebody stands something much heavier on it than you planned for.
Toughening must be specified when you order — see when safety glass is required.
Edges: always polished
Every edge of a shelf is exposed and gets handled — when you clean it, when you slide something onto it, when you reach past it. An unpolished edge on a shelf is a genuine cut hazard, not just an aesthetic problem. Read the edge guide if you want the detail.
Clear or low iron
Standard clear glass has a green cast that concentrates in the thickness, so it shows most at the edge — exactly where you look at a shelf. On 6mm it is subtle. On 10mm or 12mm it is obvious.
For a shelf inside a dark cupboard, nobody will ever notice. For a lit display shelf or a glazed cabinet, low iron is close to colourless and the difference is immediately visible side by side. See whether low iron is worth the premium.
Measuring
Measure the opening and take 2–3mm off each dimension. A shelf cut to the exact opening will not go in, and forcing glass into a tight opening is how it chips — and a chipped edge is where a break starts.
Check the opening at the front and the back. Cabinets are rarely perfectly square.
Enter your sizes on any clear glass product for an immediate price, or email us at info@affordableglassonline.com.au if the span is unusual and you want a second opinion.