Disk density

Each designation describes a set of characteristics that can affect the areal density of a disk or the efficiency of the encoded data.

Floppy drives utilize 300-oersted write heads, FM encoding, and a track width of 0.330 mm (0.0130 in) for a density of 48 tracks-per-inch (tpi) and 5,876 bits-per-inch (bpi).

The Commodore 8050 and 8250 are rare instances of drives that used 375 kbit/s GCR code instead of the usual 250 kbit/s double-density format and they could store roughly 500 kilobytes on one side of a disk.

However, drives utilize stronger 670-oersted write heads and a narrower track width of 0.115 mm (0.0045 in) for a density of 135 tpi and 8,717 bpi.

Extra-high density (ED) doubles the capacity over HD by using a barium ferrite coating and a special write head that allows the use of perpendicular recording.