The thickness of the glass, span between supports, square footage and glass type determine the amount of weight that it can support. Glass with a thickness of 3/16 inch, 1/4 inch and 1/2 inch is used for shelving. However, thicker glass is still prone to breakage due to stress.
Typically, thicker glass can support heavier weights without breaking. Even with a strong support, 1/4-inch thick glass will not hold more than 70 pounds. The standard thickness of most glasses in commercial shelves is 3/8 to 5/8 inch, which can support moderately heavy items like books. Although thicker glass can support heavy weight, short distances between support brackets help support even heavier weight.