# How much data does this 1s/2d 5.25" floppy diskette hold? **URL:** \ **Category:** Factual Questions\ **Created:** [April 16, 2013, 10:23pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884 "2013-04-16T22:23:46Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![Rucksinator](https://avatars.discourse-cdn.com/v4/letter/r/898d66/32.png) [@Rucksinator](https://boards.straightdope.com/u/Rucksinator)\ **Post date:** [April 16, 2013, 10:23pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/1 "2013-04-16T22:23:46Z")
I dug some ancient floppy disks out. \* Memorex single sided, double density 5 1/4". There is no mention on the box of mb or kb, which is what I expected because back when I used these there was only talk about sectors (IIRC, it was 20+ years ago). I checked eBay to see if this unopened box was worth anything (not really) and one listing indicated that 2S/HD was 1.2 MB. I’m guessing that HD is twice as big as 2D (double density), which would put these at about .3 MB. I didn’t get much from [wikipedia](http://en.wikipedia.org/wiki/Floppy_disk) except for this nugget: “…40‑track double-density (360 KB)…” This is really just for my own curiosity, but it’s something that I’ve been curious about for over 2 decades, since about the time I went from thinking about floppy disk capacity in terms of sectors (63, IIRC) to bytes. So, while we’re at it, how many bytes on a sector? FWIW, the computer that I used for most of the 80s was a TRS-80 64k color computer. - (Long story, but I subbed for a science teacher today and will tomorrow and the lesson is on magnets and 50 minutes is a long time to just play with magnets so I’m going to go off on a tangent with the older kids.) ---
**Author:** ![xizor](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/xizor/32/102_2.png) [@xizor](https://boards.straightdope.com/u/xizor)\ **Post date:** [April 16, 2013, 10:35pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/2 "2013-04-16T22:35:24Z")
Single sided, double density is 360kb [http://en.wikipedia.org/wiki/Floppy\_disk#5+1.E2.81.844-inch\_floppy\_disk](http://en.wikipedia.org/wiki/Floppy_disk#5+1.E2.81.844-inch_floppy_disk) ---
**Author:** ![WotNot](https://avatars.discourse-cdn.com/v4/letter/w/e19b73/32.png) [@WotNot](https://boards.straightdope.com/u/WotNot)\ **Post date:** [April 16, 2013, 10:48pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/3 "2013-04-16T22:48:42Z")
And here was me wondering how a 5.25" disk could be priced at 1 shilling and tuppence… ---
**Author:** ![Saltire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saltire/32/553_2.png) [@Saltire](https://boards.straightdope.com/u/Saltire)\ **Post date:** [April 16, 2013, 10:58pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/4 "2013-04-16T22:58:27Z")
And back in the days of the Apple ][s, we’d have the entire operating system and a few games on one of those 360K babies. Most of the single-sided ones would actually have magnetic media on both sides, with only one side tested to ensure quality control. You could use a hole punch to notch the place where the drive sensor checked for writability, and most of the time it would work as doublesided when you flipped it over. We were cheap like that. ---
**Author:** ![Rucksinator](https://avatars.discourse-cdn.com/v4/letter/r/898d66/32.png) [@Rucksinator](https://boards.straightdope.com/u/Rucksinator)\ **Post date:** [April 16, 2013, 11:24pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/5 "2013-04-16T23:24:02Z")
> [@Saltire](#): > > And back in the days of the Apple ][s, we’d have the entire operating system and a few games on one of those 360K babies… **Saltire** , back in those days, were you well aware of how many kb the disks held? Because I don’t recall reading about bytes or KB in my Rainbow magazines or in the books that came with my co-co, nor is there anything on this box of disks (or is it discs?) mentioning capacity in bytes. Is this a PC vs. Mac thing? Or is it just that capacity wasn’t measured (or mentioned) in bytes until a certain time? ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [April 16, 2013, 11:33pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/6 "2013-04-16T23:33:02Z")
things back then were not uniform, things varied from computer manufacturer to manufacturer and would even change with and within models. you would format the disk for your computer before using. you got what your machine was intended to run. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [April 16, 2013, 11:37pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/7 "2013-04-16T23:37:34Z")
> [@WotNot](#): > > And here was me wondering how a 5.25" disk could be priced at 1 shilling and tuppence… Especially when it costs thruppence and sixpence just to get on the bus. (More if it’s an MCA bus, of course, but that’s after decimalisation, which is spelt “The fuck’s a tanner again?” in the States.) ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [April 16, 2013, 11:39pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/8 "2013-04-16T23:39:52Z")
> [@Rucksinator](#): > > **Saltire** , back in those days, were you well aware of how many kb the disks held? Because I don’t recall reading about bytes or KB in my Rainbow magazines or in the books that came with my co-co, nor is there anything on this box of disks (or is it discs?) mentioning capacity in bytes. Is this a PC vs. Mac thing? Or is it just that capacity wasn’t measured (or mentioned) in bytes until a certain time? It depended on what sort of computer you put them in, IIRC. TRS-80s had different capacities than C64s and both were different than Apple II computers. (or Macs vs PCs vs Amigas a few years later with 3.5" diskettes) So they’d just label them 5.25" SS/SD or whatever. ---
**Author:** ![Saltire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saltire/32/553_2.png) [@Saltire](https://boards.straightdope.com/u/Saltire)\ **Post date:** [April 16, 2013, 11:56pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/9 "2013-04-16T23:56:01Z")
Right. In the same way that a hard drive might have different capacities depending on if you formatted it using FAT, NTFS or FAT32, floppy capacities varied a bit. Also, since you often had your OS on there (though there were certainly pure-data disks), the free space would vary depending on your OS version. I knew the 360Kb number, and 1.44Mb for 3.5-inch disks, but didn’t pay too much attention. I’d just try to write something, and if I was told the disk was full I’d stick in a different disk. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [April 16, 2013, 11:56pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/10 "2013-04-16T23:56:18Z")
> [@bump](#): > > It depended on what sort of computer you put them in, IIRC. TRS-80s had different capacities than C64s and both were different than Apple II computers. Even when the world had moved on to 3.5" non-floppy floppies, OSes could still fiddle with the drive hardware enough to put, say, 1.722 MB of data on a supposedly 1.44 MB disk. [tomsrtbt (pronounced “tom’s root boot”) does precisely that](http://www.toms.net/rb/tomsrtbt.FAQ): ```auto Virtually all 1.44 drives support 1.722 just fine, but it is possible for an extended format to break a floppy drive, use tomsrtbt at your own risk. ``` As I recall, floppy drives could be misaligned slightly relative to each other; as long as you stuck with the standard formats, this usually wasn’t a problem, but stretching things with nonstandard ones risked making disks that could only be read successfully on one machine. Frankly, though, a bigger worry, especially as floppies began to give way to thumb drives and writable CD-ROMs, was the fact floppies were often unreliable regardless of formatting. One final note: **[The 1.44 MB size is a lie regardless of how you count, because it depends on mixing two different ways of counting storage in a dishonest way](http://homepage.ntlworld.com/jonathan.deboynepollard/FGA/1mb44-is-not-a-standard-floppy-disc-size.html)**: > [@](#): > > A high capacity [90mm floppy disc](http://homepage.ntlworld.com/jonathan.deboynepollard/FGA/floppy-discs-are-90mm-not-3-and-a-half-inches.html) that is low-level formatted in the standard manner has 2 sides, 80 tracks, and 18 sectors per track. There are thus 2880 sectors on the disc. Each sector holds 0.5KiB, which is 512 bytes, meaning that the formatted data capacity of the disc is 1440KiB, which is 1474560 bytes. > > 1474560 divided by 1024 squared is 1.40635. The formatted data capacity of a 90mm high capacity floppy disc in megabinarybytes is thus (approximately) 1.41MiB. > > 1474560 divided by 1000 squared is 1.47456. The formatted data capacity of a 90mm high capacity floppy disc in megabytes is thus (approximately) 1.47MB. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [April 18, 2013, 11:15pm UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/11 "2013-04-18T23:15:23Z")
> [@bump](#): > > It depended on what sort of computer you put them in, IIRC. TRS-80s had different capacities than C64s and both were different than Apple II computers. > > (or Macs vs PCs vs Amigas a few years later with 3.5" diskettes) > > So they’d just label them 5.25" SS/SD or whatever. Good point. Other operating systems used other track formats that could put different amounts of data on the same medium. For instance, the DSDD (Double Sided Double Density) 5 1/4" floppy everyone’s talking about (360K capacity under DOS and related OSs) was 440 Kbytes when formatted for an Amiga. Of course, Amigas didn’t come with 5 1/4" drives, but they were available as an aftermarket accessory. ---
**Author:** ![1jow](https://avatars.discourse-cdn.com/v4/letter/1/dbc845/32.png) [@1jow](https://boards.straightdope.com/u/1jow)\ **Post date:** [April 19, 2013, 12:03am UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/12 "2013-04-19T00:03:14Z")
Search, how much data does a 5.5 in floppy disc hold. ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [April 19, 2013, 12:25am UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/13 "2013-04-19T00:25:11Z")
My son works for DeVry, and they have a bunch of Banker’s Boxes full of old floppies with sensitive information they no longer need to maintain. Of course, being a school of technology, they have some fancy shmancy super high tech gizmo to destroy the floppies…3 20 year old kids making minimum wage. They ripped, cracked, bent and flung their way through an entire box, and then realized they’d destroyed less than an iPad worth of memory. 😃 Fun images on the topic here: [How Many Floppy Disks Would It Take To Equal 1 Gigabyte?](http://www.techrepublic.com/photos/how-many-floppy-disks-would-it-take-to-equal-1-gigabyte/6192879) ---
**Author:** ![RaftPeople](https://avatars.discourse-cdn.com/v4/letter/r/6f9a4e/32.png) [@RaftPeople](https://boards.straightdope.com/u/RaftPeople)\ **Post date:** [April 19, 2013, 12:46am UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/14 "2013-04-19T00:46:36Z")
> [@Rucksinator](#): > > **Saltire** , back in those days, were you well aware of how many kb the disks held? Because I don’t recall reading about bytes or KB in my Rainbow magazines or in the books that came with my co-co, nor is there anything on this box of disks (or is it discs?) mentioning capacity in bytes. Is this a PC vs. Mac thing? Or is it just that capacity wasn’t measured (or mentioned) in bytes until a certain time? The trash-80 color disk system that I used had a default of 256 byte sectors, 18 sectors and 35 tracks. But I overrode all of that and created whatever varying number of sectors and sector lengths I wanted to (up to the limit of the hardware). ---
**Author:** ![Running\_with\_Scissors](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Running\_with\_Scissors](https://boards.straightdope.com/u/Running_with_Scissors)\ **Post date:** [April 19, 2013, 1:18am UTC](https://boards.straightdope.com/t/how-much-data-does-this-1s-2d-5-25-floppy-diskette-hold/655884/15 "2013-04-19T01:18:17Z")
> [@Saltire](#): > > And back in the days of the Apple ][s, we’d have the entire operating system and a few games on one of those 360K babies. It’s worth noting here that the Apple ][ diskettes (SS/SD) held only 143K. > [@Saltire](#): > > Most of the single-sided ones would actually have magnetic media on both sides, with only one side tested to ensure quality control. You could use a hole punch to notch the place where the drive sensor checked for writability, and most of the time it would work as doublesided when you flipped it over. We were cheap like that. Of course, when floppies were over $2.00 each to hold only 143K, you could spend hundreds on them, so the cheapness was justified.