A benchtop can be any thickness. The standard thickness is 3.9cm; however, this ultimately determined by your chosen material. For instance, laminate benchtops are 3.8cm thick, as too are standard timber benchtops. Yet, stone benchtops are available in various thicknesses, relative to the manufacturer.
The Silestone benchtops in our Stone Benchtop range comes in three thicknesses; 1.2cm, 2cm, and 3cm, while other stone benchtop manufacturers offer thicknesses of 2cm and 4cm.