3.5" Form Factor

The 3.5" form factor is the standard in the PC world today, and has been for about the last two decades. Drives of this size are found almost exclusively now in modern desktop PCs, and even in servers and larger machines. The only major market where other form factors hold sway over 3.5" is that for laptops and other portable devices, where the reduced size of 2.5" and smaller form factors is important.

Like the 5.25" form factor before it, the 3.5" form factor is named not for any dimension of the drives themselves, but rather for the fact that they were designed to fit into the same drive bay as 3.5" floppy disk drives. 3.5" form factor drives traditionally have used 3.74" platters with an overall drive width of 4.0" and depth of about 5.75". In recent years, 3.5" form factor drives with platters smaller than 3.74"--in some cases much smaller--have appeared on the market. See the discussion of platter size for more details.

It is likely that the 3.5" form factor will continue to be the industry standard in PCs for years to come, due to the enormous installed base of systems that use this size, and no real compelling reason to change the form factor for the typical desktop machine.

Next: 2.5" Form Factor