My used and available storage don't add up

Hello Thecails,

Thank you for the question. I found an article with information about the discrepancy you may see between the reported usage on your iPad and the expected 16 GB. The difference you are seeing has to do with how the applications report the usage as well as the basic iOS software that installed on your device:

Understanding storage capacity in iPad, iPhone, iPod

When you view the storage capacity of your iPod, iPhone, iPad, or other electronic devices within its operating system, the capacity is reported using the the binary system (base 2) of measurement. In binary, 1 GB is calculated as 1,073,741,824 bytes.

For example: The way decimal and binary numeral systems measure a GB is what causes a 32 GB storage device to appear as approximately 28 GB when detailed by its operating system, even though the storage device still has 32 billion bytes (not 28 billion bytes), as reported.

You can see this difference if you look at how your computer summarizes the capacity of your iPod, iPad, or iPhone’s storage when the device is connected to your computer. You will also see this difference in the About menu on your iPod, iPad, or iPhone. The important point to understand is that the available storage capacity is the same no matter which system (decimal or binary) is used. Nothing is missing.

The storage media in your Apple product, like all storage devices, uses some of its capacity for formatting, so actual capacity available for applications and files will be less. In addition, other factors, such as pre-installed systems or other software and media, will also use part of the available storage capacity.

Find the full article here:

How OS X and iOS report storage capacity

http://support.apple.com/kb/TS2419

Thank you for using Apple Support Communities.

Best,

Sheila M.