Depending on your glass usage, you will need a specific thickness of glass.
1/16" is often used for light window repair such as in a garage.
1/8" is often used in framed mirrors, stationary windows or cabinet glass.
1/4" is often used for wall mirrors, and glass to protect existing furniture such as a tabletop.
3/8" is often used in shelving for heavy objects.
Glass heavier than 3/8", such as 1/2" is used as pieces of furniture.