11

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

a bunch of 3.5inch floppy disks

15
  • 17
    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. Jun 15 '21 at 15:01
  • 4
    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. Jun 15 '21 at 15:14
  • 7
    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 '21 at 15:47
  • 15
    Depends: European or African? Jun 16 '21 at 12:49
  • 3
    @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!) Jun 16 '21 at 15:38
36
+50

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 431 floppy disks (3.5-inch) from several brands such as 3M, BASF, Dixons, Fujifilm, HEMA, IBM, Imation, INMAC, Maxell, MCN, Mitsubishi, Nashua, Sony, TDK, Verbatim and types (DD/HD). Of the measured set 64% contained a printed label and 36% did not. 91% of the set was of the type HD and 9% of the type DD.

The result: One 3.5-inch floppy disk weighs between 15 - 25 grams. The average (mean) weight of one 3.5-inch floppy disk is 18 grams, the median is 17 gram. Of that weight 96% is estimated to consist of the plastic housing and paper ring only.

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

Below you'll find the raw data (in CSV format) as requested in the comments. It contains the brand and production country if available, if the disk contained a paper label and what type of disk 3.5-inch disk it was (HD or DD). As requested the standard deviation is 2.1. The method used was a kitchen scale (see photo below), set to 0 before measuring:

Brand;ProductionCountry;LabelPasted;HD/DD;Grams
Unknown;Unknown;Yes;HD;18
Unknown;Unknown;Yes;HD;19
Verbatim;Unknown;No;HD;18
Unknown;Germany;Yes;HD;20
Unknown;Unknown;Yes;HD;21
Unknown;Germany;Yes;DD;21
Unknown;Unknown;No;HD;16
MCN;Unknown;Yes;DD;21
BASF;Unknown;Yes;HD;19
Unknown;Unknown;Yes;HD;18
Unknown;Japan;No;HD;21
Unknown;Germany;Yes;HD;19
Unknown;Unknown;Yes;HD;19
Unknown;Germany;Yes;HD;25
Unknown;Germany;Yes;HD;21
Unknown;Unknown;Yes;HD;18
Unknown;Germany;Yes;HD;20
3M;Unknown;No;HD;21
Unknown;Unknown;Yes;HD;20
Unknown;Germany;Yes;DD;21
Unknown;Germany;Yes;DD;21
3M;Unknown;Yes;DD;20
3M;Unknown;Yes;DD;22
3M;Unknown;Yes;DD;22
3M;Unknown;Yes;DD;22
3M;Unknown;Yes;DD;22
3M;Unknown;Yes;DD;22
3M;Unknown;Yes;DD;22
3M;Unknown;Yes;DD;23
Unknown;Germany;Yes;DD;21
Unknown;Germany;Yes;DD;21
Unknown;Germany;Yes;DD;20
Maxell;Japan;Yes;DD;21
Maxell;Japan;Yes;DD;22
Maxell;Japan;Yes;DD;21
Fujifilm;Germany;Yes;DD;19
Nashua;Japan;Yes;DD;21
Nashua;Japan;Yes;DD;22
Nashua;Japan;Yes;DD;21
Nashua;Japan;Yes;DD;22
Nashua;Japan;Yes;DD;21
Nashua;Japan;Yes;DD;22
Unknown;U.S.A.;No;DD;21
Unknown;Unknown;Yes;DD;21
Unknown;Unknown;Yes;DD;22
Unknown;Unknown;Yes;DD;21
Unknown;Unknown;Yes;DD;22
MCN;Unknown;Yes;DD;21
MCN;Unknown;Yes;DD;20
INMAC;Unknown;Yes;DD;21
Unknown;Unknown;Yes;DD;21
BASF;Unknown;Yes;DD;23
Unknown;Unknown;Yes;DD;21
Unknown;Unknown;Yes;DD;22
Unknown;Unknown;Yes;DD;22
Unknown;Germany;Yes;DD;19
Unknown;E.C.;Yes;DD;17
3M;Unknown;No;HD;21
Unknown;Unknown;No;HD;21
Unknown;E.C.;No;HD;17
Unknown;Unknown;No;HD;20
Unknown;E.C.;No;HD;20
Unknown;Germany;No;HD;17
Unknown;Germany;No;HD;17
Unknown;Germany;No;HD;17
Unknown;Unknown;No;HD;18
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;21
Unknown;Unknown;No;HD;17
Unknown;Germany;No;HD;17
Unknown;Unknown;No;HD;18
Unknown;E.C.;No;HD;17
Unknown;Unknown;No;HD;17
Unknown;Unknown;No;HD;19
Unknown;E.C.;No;HD;17
Unknown;Unknown;No;HD;17
Unknown;Unknown;No;HD;17
Unknown;Unknown;No;HD;17
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;18
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;21
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;18
Unknown;Japan;No;HD;21
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;22
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;21
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;20
Unknown;Japan;No;HD;20
Unknown;Unknown;No;HD;21
Imation;Unknown;No;HD;17
Imation;Unknown;Yes;HD;17
Imation;Unknown;Yes;HD;17
Imation;Unknown;Yes;HD;18
Imation;Unknown;Yes;HD;17
Imation;U.S.A.;No;HD;16
Imation;U.S.A.;No;HD;16
Imation;U.S.A.;No;HD;16
Imation;U.S.A.;Yes;HD;18
Imation;U.S.A.;Yes;HD;17
Imation;U.S.A.;Yes;HD;17
Imation;U.S.A.;Yes;HD;16
Imation;U.S.A.;Yes;HD;16
Imation;Unknown;No;HD;16
Imation;Unknown;No;HD;16
Imation;U.S.A.;Yes;HD;17
Imation;U.S.A.;No;HD;16
Imation;U.S.A.;Yes;HD;18
Imation;U.S.A.;No;HD;18
Imation;U.S.A.;Yes;HD;17
Imation;Unknown;Yes;HD;18
Imation;Unknown;No;HD;16
Imation;Unknown;Yes;HD;16
3M;Unknown;Yes;HD;20
3M;Unknown;Yes;HD;21
3M;Unknown;Yes;HD;20
3M;Unknown;Yes;HD;21
3M;Unknown;Yes;HD;20
3M;Unknown;Yes;HD;20
3M;Unknown;Yes;HD;21
3M;Unknown;Yes;HD;20
3M;Unknown;Yes;HD;21
3M;Unknown;Yes;HD;21
3M;Unknown;Yes;HD;20
3M;Unknown;Yes;HD;21
3M;Unknown;Yes;HD;21
3M;Unknown;Yes;HD;20
3M;Unknown;Yes;HD;19
3M;Unknown;Yes;HD;17
3M;Unknown;Yes;HD;19
Imation;U.S.A.;No;HD;16
Imation;U.S.A.;Yes;HD;17
Imation;U.S.A.;Yes;HD;17
Imation;U.S.A.;Yes;HD;18
Imation;U.S.A.;Yes;HD;17
Imation;Unknown;No;HD;18
Imation;Unknown;No;HD;18
Imation;Unknown;No;HD;18
Imation;Unknown;No;HD;18
Imation;Unknown;No;HD;17
Sony;Unknown;No;HD;17
Sony;Unknown;No;HD;17
Sony;Unknown;No;HD;18
Sony;Unknown;No;HD;18
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;20
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;23
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;19
Sony;Unknown;Yes;HD;18
TDK;Unknown;No;HD;20
TDK;Unknown;No;HD;21
TDK;Unknown;No;HD;21
TDK;Unknown;Yes;HD;22
TDK;U.S.A.;Yes;HD;22
TDK;U.S.A.;Yes;HD;21
TDK;U.S.A.;Yes;HD;22
TDK;U.S.A.;Yes;HD;22
TDK;U.S.A.;Yes;HD;21
TDK;U.S.A.;Yes;HD;21
TDK;U.S.A.;Yes;HD;22
TDK;U.S.A.;Yes;HD;22
TDK;Unknown;No;HD;16
TDK;Unknown;Yes;HD;15
TDK;Unknown;Yes;HD;16
TDK;Unknown;Yes;HD;16
TDK;Unknown;Yes;HD;15
TDK;Unknown;Yes;HD;16
TDK;Unknown;Yes;HD;15
TDK;Unknown;Yes;HD;16
TDK;Unknown;Yes;HD;15
TDK;Unknown;Yes;HD;17
TDK;Unknown;Yes;HD;16
TDK;Unknown;Yes;HD;16
TDK;Unknown;Yes;HD;16
TDK;Unknown;Yes;HD;16
Dixons;E.C.;No;HD;17
Dixons;E.C.;No;HD;17
Dixons;E.C.;No;HD;16
Dixons;E.C.;No;HD;16
Dixons;E.C.;No;HD;16
Dixons;E.C.;No;HD;16
Dixons;E.C.;No;HD;16
Dixons;E.C.;No;HD;16
Dixons;E.C.;No;HD;16
Dixons;E.C.;No;HD;16
Dixons;E.C.;No;HD;16
Dixons;E.C.;No;HD;16
Dixons;E.C.;No;HD;16
Unknown;Unknown;Yes;HD;16
Dixons;E.C.;Yes;HD;17
Dixons;E.C.;Yes;HD;17
Dixons;E.C.;Yes;HD;17
Dixons;E.C.;Yes;HD;17
Dixons;E.C.;Yes;HD;18
Dixons;E.C.;Yes;HD;17
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;17
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;17
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;17
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;17
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;16
Dixons;E.C.;Yes;HD;17
MCN;Japan;Yes;HD;21
MCN;Japan;Yes;HD;21
MCN;Japan;Yes;HD;21
MCN;Japan;Yes;HD;21
MCN;Japan;Yes;HD;21
TDK;E.C.;Yes;HD;16
TDK;E.C.;Yes;HD;16
TDK;Unknown;Yes;HD;17
TDK;Unknown;Yes;HD;18
TDK;Unknown;Yes;HD;18
TDK;Unknown;Yes;HD;17
TDK;Unknown;Yes;HD;18
TDK;Unknown;Yes;HD;17
TDK;Unknown;Yes;HD;18
TDK;Unknown;Yes;HD;17
TDK;Unknown;Yes;HD;18
TDK;E.C.;No;HD;17
TDK;E.C.;No;HD;17
TDK;E.C.;No;HD;17
TDK;E.C.;No;HD;16
TDK;E.C.;No;HD;15
TDK;E.C.;No;HD;16
TDK;E.C.;No;HD;16
TDK;E.C.;No;HD;15
TDK;E.C.;No;HD;15
TDK;E.C.;No;HD;16
TDK;E.C.;No;HD;16
TDK;E.C.;No;HD;16
TDK;E.C.;No;HD;16
TDK;E.C.;No;HD;16
TDK;E.C.;No;HD;16
TDK;E.C.;No;HD;16
TDK;E.C.;No;HD;16
Maxell;England;Yes;HD;15
Unknown;Unknown;Yes;HD;16
Unknown;Unknown;Yes;HD;20
BASF;Unknown;Yes;HD;16
IBM;Japan;Yes;HD;20
Mitsubishi;Japan;Yes;HD;21
Mitsubishi;Japan;Yes;HD;20
Mitsubishi;Japan;Yes;HD;21
Unknown;Japan;Yes;HD;21
Fujifilm;Germany;Yes;HD;17
Fujifilm;Germany;Yes;HD;16
Fujifilm;Germany;Yes;HD;17
Fujifilm;Germany;Yes;HD;17
Fujifilm;Germany;Yes;HD;17
Fujifilm;Germany;Yes;HD;17
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;19
Unknown;Unknown;No;HD;20
Unknown;Unknown;No;HD;16
Unknown;E.C.;No;HD;17
Unknown;E.C.;No;HD;16
Unknown;E.C.;No;HD;16
Unknown;E.C.;No;HD;16
Unknown;E.C.;No;HD;17
Unknown;England;Yes;HD;18
Unknown;Germany;Yes;HD;16
Unknown;Germany;Yes;HD;16
Unknown;E.C.;Yes;HD;17
Unknown;E.C.;Yes;HD;17
Unknown;E.C.;Yes;HD;17
Unknown;Unknown;Yes;HD;16
Unknown;Unknown;Yes;HD;16
Unknown;Unknown;Yes;HD;17
Unknown;Unknown;Yes;HD;17
Unknown;Unknown;Yes;HD;16
Unknown;Unknown;Yes;HD;18
Unknown;Unknown;Yes;HD;18
Unknown;Unknown;Yes;HD;17
Unknown;Unknown;Yes;HD;20
Unknown;Unknown;Yes;HD;17
Unknown;Unknown;Yes;HD;21
3M;Unknown;Yes;HD;17
3M;Unknown;No;HD;17
BASF;Unknown;No;HD;17
BASF;Unknown;No;HD;17
BASF;Unknown;No;HD;16
BASF;Unknown;Yes;HD;17
BASF;Unknown;Yes;HD;16
BASF;Unknown;Yes;HD;16
BASF;Unknown;Yes;HD;17
HEMA;Unknown;Yes;HD;18
HEMA;Unknown;Yes;HD;16
HEMA;Unknown;Yes;HD;16
HEMA;Unknown;Yes;HD;18
HEMA;Unknown;No;HD;16
HEMA;Unknown;No;HD;16
HEMA;Unknown;No;HD;17
Verbatim;Unknown;Yes;HD;18
Verbatim;Unknown;Yes;HD;18
Verbatim;Unknown;Yes;HD;18
Verbatim;Unknown;Yes;HD;18
Verbatim;Unknown;Yes;HD;18
Verbatim;Unknown;Yes;HD;18
Verbatim;Unknown;Yes;HD;19
Fujifilm;Germany;Yes;HD;16
Fujifilm;Germany;No;HD;15
Fujifilm;Germany;No;HD;16
Fujifilm;Germany;No;HD;15
Fujifilm;Germany;No;HD;16
Fujifilm;Germany;No;HD;15
Fujifilm;Germany;No;HD;16
Fujifilm;Germany;No;HD;16
Fujifilm;Germany;No;HD;15
Imation;Unknown;No;HD;16
Imation;Unknown;No;HD;17
Imation;Unknown;No;HD;16
Imation;Unknown;No;HD;15
Imation;Unknown;No;HD;16
Imation;Unknown;No;HD;15
Imation;Unknown;No;HD;16
Imation;Unknown;No;HD;16
Imation;Unknown;No;HD;16
Sony;Unknown;No;HD;17
Sony;Unknown;No;HD;16
Sony;Unknown;No;HD;16
Sony;Unknown;No;HD;16
Sony;Unknown;No;HD;17
Sony;Unknown;No;HD;17
Sony;Unknown;No;HD;16
Sony;Unknown;No;HD;16
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;16
Sony;Unknown;Yes;HD;17
Sony;Unknown;Yes;HD;17
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;17
Sony;Unknown;Yes;HD;17
Sony;Unknown;Yes;HD;17
Sony;Unknown;Yes;HD;17
Sony;Unknown;Yes;HD;17
Sony;Unknown;Yes;HD;18
Sony;Unknown;Yes;HD;16
Sony;Unknown;Yes;HD;16
Sony;Unknown;Yes;HD;17
Sony;Unknown;Yes;HD;16
Sony;Unknown;Yes;HD;17
Sony;Unknown;Yes;HD;16
Sony;Unknown;Yes;HD;17
Unknown;E.C.;No;HD;18
Unknown;E.C.;No;HD;18
Unknown;E.C.;No;HD;18
Unknown;E.C.;No;HD;18
Unknown;E.C.;No;HD;18
Unknown;Unknown;No;HD;16
Unknown;Germany;Yes;HD;16
Unknown;Germany;Yes;HD;16
Unknown;Germany;Yes;HD;16
Unknown;Germany;Yes;HD;16
Unknown;Germany;Yes;HD;15
Unknown;E.C.;Yes;HD;16
Unknown;E.C.;Yes;HD;16
Unknown;E.C.;Yes;HD;16
Unknown;E.C.;Yes;HD;16
Unknown;E.C.;Yes;HD;16
Unknown;E.C.;Yes;HD;17
Unknown;E.C.;Yes;HD;16
Unknown;E.C.;Yes;HD;16
Unknown;E.C.;Yes;HD;17
Unknown;E.C.;Yes;HD;15
Unknown;E.C.;Yes;HD;15
Unknown;E.C.;Yes;HD;15
Unknown;E.C.;Yes;HD;16
Unknown;E.C.;Yes;HD;16
Unknown;E.C.;Yes;HD;16
Unknown;Unknown;Yes;HD;18
Unknown;Unknown;Yes;HD;16
Unknown;Unknown;Yes;HD;16
Unknown;Unknown;Yes;HD;19
Unknown;Unknown;Yes;HD;20
Unknown;Unknown;Yes;HD;20
Unknown;Unknown;Yes;HD;20
Unknown;Unknown;Yes;HD;20
Unknown;Unknown;Yes;HD;16
Unknown;Unknown;Yes;HD;17
Unknown;Unknown;Yes;HD;19
Unknown;Unknown;Yes;HD;19
Unknown;Unknown;Yes;HD;18
Unknown;Unknown;Yes;HD;17

scale model scale

Additionally regarding the independent parts of a floppy based on a handful of parts I've had laying around. I've measured 5 hubs which had a total of 11 grams, averaging out to 2.2 grams each. That would mean the hub alone is roughly 1% of the floppy weight. I've measured 8 floppy shutters with a total weight of 22 gram, averaging out to 2,75 gram per floppy. The hubs seem to be metal when using a magnet and the shutters seem to be aluminium. The housing + paper ring combined of 4 floppies total is 60 gram which is 15 gram on average per floppy. The magnetic disk and spring (out of experience) weigh almost nothing. So we can estimate that roughly 96% of the weight is the plastic housing + paper ring, 3% shutter + hub and maybe 1% for other parts (spring, magnetic disk, write protect tab, label).

floppy parts

12
  • 12
    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 '21 at 12:01
  • 11
    A customer might expect a "double density" disk of the same size to be twice as heavy.
    – JDługosz
    Jun 16 '21 at 20:55
  • 4
    @JDługosz even more with compressed files are stored :)
    – Raffzahn
    Jan 1 at 19:59
  • 1
    1.61 µg/bit (I expected them to be heavier) ;)
    – tofro
    Jan 1 at 22:47
  • 1
    @Zac67 I tend to be pretty precise when I'm not joking;)
    – tofro
    Jan 2 at 17:49

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