Data Density

Following question driven by seeing a box of floppy discs in tech room.

Question: How large would the floppy disk have to be to hold a hard drive of content?


  • A floppy disk holds 1.44 MB
  • The largest consumer hard drive is 2 TB

Size of a desk? room? building? field? town?

Extension 1: What about a CD or a DVD?

Extension 2: How small could the hard drive be if it only held a floppy disk of material?

any more?

Revision: 10/1/10 (or 22 to CS geeks)

Answer!  Highlight the text below to find the answer to the first question.

The floppy disk with a size of 2 TB would have a radius of about 47 meters.

Here’s a picture showing how large it would be:

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4 Responses to Data Density

  1. great question. Maybe also pair this with a phonograph record, and show the excellent electron micrographs of a phonograph groove. Then kids could look at CD and electron micrographs of CD pits as well.

    I really like this—could be used in a math or science class.

    • Dan says:

      Good call. A good CS question could be to ask how many pits are possible on the CD. I know there is some kind of error correction, but I’m not sure the ratio of real data to raw data.

  2. Pingback: Tweets that mention Data Density « A Recursive Process --

  3. Dan says:

    FYI, I’ve amended the original post with an answer to the first question.

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