What is the weight of a 3.5 inch floppy disk and was the weight ever standardized?

a bunch of 3.5inch floppy disks

  • 13
    Why do you think that the mass might be standardised, especially of the whole package? I could understand some standardisation for the disk itself (or more specifically its moment of inertia about the spindle axis), but even that seems unlikely, as drives will just take longer to spin up heavier disks than lighter ones. It's actually a differentiating feature (build quality against speed against cost) of different brands. – Toby Speight Jun 15 at 15:01
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    What’s more, there’s quite a lot of scope for variation: the rotating disk itself probably won’t vary much, but the rigid package can, the larger disk at the centre also can, metal shutters weigh more than plastic shutters, different types of spring can be used, and some disks even had protective coating inside the rigid package which would add (a little) weight. – Stephen Kitt Jun 15 at 15:14
  • 6
    Some disks hold more data than others. Therefore it is logical to conclude that Double Density disks must weigh more than Single Density disks, right? ;^) – Geo... Jun 15 at 15:47
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    Depends: European or African? – Carl Witthoft Jun 16 at 12:49
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    @ReversedEngineer, That depends on whether you think that "disk" refers to the circular piece of coated mylar film that is contained within the assembly, or whether you think it refers to the entire assembly. The mylar film certainly is floppy (Don't ask me how I know!) – Solomon Slow Jun 16 at 15:38

For the sake of information available on the internet (as I wasn't able to find the answer elsewhere) I have just measured the weight of 306 3.5-inch floppy disks from several random brands. The measurement did not take into account that some floppy disks had paper labels pasted on it, while most had not.

The result: One 3.5-inch floppy disk weighs between 17-22 grams. The average weight of one 3.5-inch floppy disk is 19 grams.

Regarding the standardization: I could not find any information that indicates there has been a standardized weight for 3.5-inch floppy disks.

  • 5
    Also it wouldn't have made too much sense to standardize the weight as an additional limit. These standards are (mostly) about cross-compatibility, and a couple grams more or less (or even double the weight) would hardly hurt the readers – Hobbamok Jun 16 at 12:01
  • 2
    A customer might expect a "double density" disk of the same size to be twice as heavy. – JDługosz Jun 16 at 20:55

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