A sorted list of all the different form factors.
Motherboard Form Factors[edit | edit source]
The smallest of the common motherboard form factors at 170 mm x 170 mm (6.7" x 6.7").
Smaller than ATX at 244 mm x 244 mm (9.6" x 9.6")
ATX[edit | edit source]
ATX is the most well known motherboard form factor, at 305 mm x 244 mm. (12" x 9.6")
E-ATX[edit | edit source]
Not backed by any standard, normally used for anything taller than ATX.
Same size as E-ATX, but is actually kept that size instead of the weird sizes E-ATX can possess on consumer platforms.
Storage Form Factors[edit | edit source]
3.5"[edit | edit source]
Based on the diameter of floppy disks as HDDs of that form factor fit in the same space as a floppy drive for 3.5" floppy disks. Though the rotation disk stack inside a 3.5" HDD is also 3.5" like it was with 3.5" floppies
2.5"[edit | edit source]
Was introduced for smaller and portable devices like laptops and was only used for HDDs in the beginning, but is now the most common form factor for SSDs.
M.2[edit | edit source]
Listed here as a storage form factor, which it actually isn't, it is an universal form factor for many different devices types including but not limited to storage. Not to be confused with the electrical/physical interface which shares the same name.