About Actual Memory Size for a USB drive

If you have ever come across a USB flash drive before, you will probably have noticed that they are often advertised by a set memory size which usually ranges anywhere from 128MB – 256 GB.  While this is the case, when you insert a USB stick into a computer you’ll often find that the storage space you actually have on the device doesn’t quite match up to what was originally advertised. This is something our customers question us about quite frequently, as for many a 32GB USB should be just that, 32GB in storage space.

Where does the loss of storage space occur?

The storage loss is down primarily to the way in which a computer naturally reads data and how manufacturers choose to advertise storage capacities. While we would perceive 1 kilobyte of data is equal to 1000 bytes this isn’t exactly accurate due to the way in which data is stored using binary code on a computer (think 1 and 0’s), which means that 1 kilobyte is actually equal to 1024 bytes so not a rounded amount as we would assume. The common prefixes therefore are

  • 1 Kilobyte (KB) = 1,024 Bytes
  • 1 MegaByte (MB) = 1,024 Kilobytes or 1,048,576 Bytes
  • 1 Gigabyte (GB) = 1,024 Megabytes or 1,073,741,824 Bytes

Because these numbers are not necessarily pretty to look at, manufacturers decide to rate most flash drive capacities on standard base 10 numbers so as per the above where 1 Mb = 1,000Kb or 1,000,000 Bytes, this means that for each 1Mb of data there is essentially 24Kb or 48,576 Bytes that is not accounted for. While this is barely noticeable on flash drives with low memory, those with much higher storage capacity see an increase in the discrepancy between the actual storage space and what is advertised.

What is the actual storage loss on a USB stick

The actual storage loss on a USB device is roughly 7% of the overall memory size, so for a 32GB device you can expect a loss of around 2GB. This, unfortunately, is a scalable loss as well, so the more memory size on a USB the more storage you will likely lose. The actual memory size of your USB flash drive is always marginally less than advertised regardless of the overall storage of the device.

Below is a chart which details the actual storage you get when using a USB stick as well as the overall loss you can expect to see.

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