Floppy Disk Size

By Deane Barker on May 13, 2004

Floppy disk: From Wikipedia we get the reason 5 1/4” floppy disks were that size.

After meeting in a bar in Boston, Adkisson asked Wang what size he thought the disks should be, and Wang pointed to a napkin and said “about that size”. Adkisson took the napkin back to California, found it to be 5¼ inches wide (13 cm), and developed a new drive of this size storing 110 KB.

A great and informative article all-around.



  1. Sorta like the story of why the pitchers mound is not some even number. Mind you I’m not a big baseball fan but someone measuring out the distance wrong then having them stick with it is pretty weird.

    take care.

  2. Reminds me of (yet) another story like this one, which I heard from someone who has worked for Philips’ “NatLab” (Physics Lab). When Philips and Sony were developing what we now know as the CD/CD-ROM, they had to decide what size it should get. Some guy at Philips thought that a diameter of 10 centimeters would be nice (serving space for about 50 minutes of music, if I’m correct), but then someone else decided that Beethoven’s 9th symphonie (“Alle Menschen werden Brüder”) should fit on it, The longest version they could think of was about 60 minutes, so the CD has to be a bit larger than the original 10 cm. Finally, some guy at Sony, a connoisseur of classical music, told them about a version that lasted for 74 minutes — giving rise to the current, weird number of 74 minutes of audio data :-)

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