A 16GB iPad has approximately 14GB of space.
So on an iPad, specs are based on actual count and usage uses the number 1024 for all conversions in computers. Thus 16,000,000,000 bytes, = 16,000,000,000/1024 to get 14GB.
There are multiple legal ways of defining bytes, kilobytes, megabytes, gigabytes, terabytes, etc.
A standard kilobyte (KB) is defined as 1024 bytes. But drive manufacturers use the more ‘lean’ definition of kilobyte, which is a very strict 1000 bytes, as opposed to 1024 bytes.
http://compreviews.about.com/od/storage/a/ActualHDSizes.htm
At some point in time, most users have come across a situation where a drive or disk being used run out of space even though there is thought to be plenty of space. A lot of times, this is the rude awakening for the consumer that the device they are attempting to store data on is not as large as it was advertised. In this article, we take a look at how manufacturers rate the capacity of storage devices such as hard drives, floppies, flash media and compact disks and their actual size.
Bits, Bytes and Prefixes.
All computer data is stored in a binary format as either a one or zero. Eight of these bits together for the most commonly referred to item in computing, the byte. The various amounts of storage capacity are referred by a prefix to represent a specific amount, similar to the metric prefixes. Since all computers are based on binary math, these prefixes represent base 2 amounts. Each level is an increment of 2 to the 10th power or 1,024. The common prefixes are as follows:
Kilobyte (KB) = 1,024 Bytes
MegaByte (MB) = 1,024 Kilobytes or 1,048,576 Bytes
Gigabyte (GB) = 1,024 Megabytes or 1,073,741,824 Bytes
Terabyte (TB) = 1,024 Gigabytes or 1,099,511,627,776 Bytes
This is very important information because when a computer operating system or program reports the available space on a drive, it is going to report the overall total of available bytes or reference them by one of the prefixes. So, an OS reporting a total space of 70.4 GB actually has around 75,591,424,409 Bytes of storage space.
Advertised vs. Actual
Since consumers don’t think in base 2 mathematics, manufacturers decided to rate most drive capacities based on the standard base 10 numbers we are all familiar with. Therefore, one Megabyte equals one million bytes while one Gigabyte equals one billion bytes. This isn’t too much of a problem with fairly small numbers such as a Kilobyte, but each level of increase in the prefix also increased the total discrepancy of the actual space compared to the advertised space.
Here is a quick reference to show the amount that the actual values differ compared to the advertised for each common referenced value:
Megabyte Difference = 48,576 Bytes
Gigabyte Difference = 73,741,824 Bytes
Terabyte Difference = 99,511,627,776 Bytes
