Answer: 8 Inches

The original floppy disk, a storage media made from a flexible and thin magnetic disk enclosed in a plastic wrapper, was invented in the late 1960s and produced commercially by IBM in 1971. The first disks were a whopping 8 inches across and stored 1.2 MB of data if optimally configured.

While the large floppy disks saw plenty of use in government, research, and large commercial institutions, such as serving as boot disks for mainframe computers, the market penetration outside of such applications was limited. The majority of consumers both in the home and in small businesses simply didn’t need such a (for the time) large capacity disk and didn’t adopt floppy drives until the introduction of the 5.25 inch disk that accompanied the first wave of affordable personal computers.

Floppy disks, first in the 5.25 inch size and then in the 3.5 inch size, were the portable storage media of choice throughout the 1980s and early 1990s. The rise of the CD-ROM in the 1990s and flash-based USB drives in the early 2000s ushered in the demise of the floppy disk. By the mid-2000s, it was rare to see an off-the-shelf desktop computer with a floppy drive.