Shower Door Glass Thickness (Inches)
US shower glass is sold and measured in fractional inches — 1/4", 3/8", and 1/2" are the three sizes that matter for seal shopping.
1/4" (0.25 in) is standard for framed doors and most big-box sliding shower doors.
3/8" (0.375 in) is the most common frameless shower door thickness — the balance of weight, rigidity, and price most manufacturers land on.
1/2" (0.5 in) shows up on heavier frameless doors and large fixed panels, where more glass weight is needed for rigidity without a frame.
Always measure your own glass with calipers before buying a seal — door thickness varies by manufacturer and installation age, and a seal sized for the wrong thickness will either not grip or won't seal properly.