Why are manufacturers allowed to make false claims about memory capacity of thumbdrives?
<p>I have a number of thumb drives and hard drives.  One hard drive I bought was said to be 2TB but its actual capacity is about 1.8 TB. A couple of thumb drives I got say they are 16 GB but on the back say:</p>

<blockquote>
  <p>1MB = 1,000,000 bytes / <br>
  1GB = 1,000,000,000 bytes</p>
</blockquote>

<p>This definition is the reason why I've accepted the false advertising on hard drive space, even though conventionally:</p>

<p>1KB = 1024 bytes<br>
1MB = 1024x1024 bytes<br>
1GB = 1024x1024x1024 bytes</p>

<p>and not</p>

<p>1KB = 1000 bytes<br>
1MB = 1000x1000 bytes<br>
1GB = 1000x1000x1000 bytes</p>

<p>As we get to higher levels the amount of space that is lost by this rounding down increases.</p>

<p>But isn't this still false advertising?  E.g., in Australia could I get a refund as I was misled in the believe that a thumb/hard drive had the higher capacity?</p>

<p>It's not the manufacturers who are wrong. <em>Your</em> definitions of KB, MB, and GB are incorrect. See, for example, <a href="http://physics.nist.gov/cuu/Units/binary.html" rel="noreferrer">NIST</a>. The numbers they are using are not "rounded down," they are the proper standardized definitions of those terms. 1024 bytes is properly termed a <em>kibibyte</em> (or KiB), not a kilobyte. 1024 kibibytes is a <em>mebibyte</em>, MiB. 1024 mebibytes is a <em>gibibyte</em>, GiB. These are defined in an international standard, IEC 80000-13 (part of the ISO series of standards defining units); "kilobyte" refers to 1000 bytes, "megabyte" to 1000000, and "gigabyte" to 1000000000. It's not lying to use units correctly, and that's what the manufacturers are doing.</p>

<p>As well as the accepted answer, don't forget that the reason your drive is reporting free space below the capacity, is dependent on what disk format you have used (or was done for you).  Even a basic boot sector, partition map and root directory may take away hundreds of MB on a sufficiently large capacity drive.</p>

<p>There will be a difference in the 'free' space if you format a drive using FAT32 or NTFS or ZFS or [insert other filing system here].</p>

<p>Back in the last days of MS-DOS, 3.5" installation disks used a special format that would actually store 1.6MB instead of the more normal 1.44MB that you got from FAT12/16, by reducing the size of the root directory (amongst other tricks).</p>

<p>Almost all of the flash memory chips used in thumb drives hold a power-of-two number of 528-byte pages; in each page, 512 bytes are used to hold user data while the remainder are used for error-correction and bookkeeping.  Some pages will be marked as defective by the manufacturer, and others are used as "slack space".  The way flash memory chips work, doesn't allow the data in individual pages to be directly replaced.  Instead, it's necessary to perform updates by writing new pages without immediately erasing old ones, and periodically relocate useful pages so as to allow for block-erase operations to erase larger chunks of old pages as a group.  In many cases, a willingness to set aside more slack space can improve performance, and a desire to maximize storage efficiency will impede performance.  A manufacturer could make a "two gigabyte" thumb drive that holds 2,000,000,000 bytes of user data just as cheaply as one that holds about 1,800,000,000 bytes of user data, but at the cost of performance and reliability.  Having better performance is more useful.</p>

<p>Of course, this is assuming the manufacturer and seller aren't crooks.  A lot of "32GiB" thumb drives are actually much smaller drives whose formatting is corrupted to make them appear bigger, but which actually means they can't hold <em>anything</em> reliably.</p>

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