How much free storage in a 16GB iPad?

No, this isn't a "who's buried in Grant' tomb" question. Rather: How much space for apps, music, etc is available on a fresh-out-of-the-box 16GB iPad? My 64GB iPad says that its "capacity" is 58.12 GB, which suggests that almost 8GB is taken up by disk formatting and the OS. That wouldn't leave much for other stuff on a 16GB. I'm providing "pre-sales tech support" for a price-sensitive relative; any data out there? Thanks!

On iOS 5 you should expect to have about 13.75 GB for items you choose to store on any 16 GB iOS device. On iOS 4 it was slightly higher - slightly over 14 GB.

Storage device manufacturers measure capacity using the decimal system (base 10), so 1 gigabyte (GB) is calculated as exactly 1,000,000,000 bytes. The capacity of the storage media in your Mac, iPad, iPod, iPhone and other Apple hardware is measured using this decimal system. This is detailed on product packaging and online through the statement "1 GB = 1 billion bytes."

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.

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