We will be using US format numbers throughout this document, as they are what is generally used in the external documentation that this is based upon.  Commas represent thousands, millions, billions, etc.  Periods represent decimal numbers.

One Thousand (10³ or 10^3 or ten to the power of three) = 1,000
One Million (10⁶ or 10^6) = 1,000,000

One Tenth (1/10) = 0.1
One Quarter (1/4) = 0.25

File Size

In computer terminology the basic unit of data is the bit. It is either a 1 or a 0, and enough bits put together can represent any data in the computer.

Everything is represented in terms of bits, which are either 0 or 1, so if you have two bits there are 2² (2^2 or two to the power of two) possible combinations: 00, 01, 10, 11.  Three bits is 2³ with possible combinations: 000, 001, 010, 011, 100, 101, 110, 111.  Four bits has 2⁴ possible combinations, Eight bits has 2⁸ and on up.  This is called "binary notation" where there are only two digits (0 and 1) as opposed to decimal noation which has ten digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9). 

A byte is a collection of bits, 8 bits to be precise (00000000, 00000001, 01110101, and 11111111 are some of the 256 possible combinations). This is the standard unit that will be used to say how much space a piece of data takes up. (e.g. that text file is 300 Bytes large, that picture is 2 million bytes, etc)

Because computers can use HUGE numbers of bytes for different things, we have a set of prefixes that we use to talk about groups of bytes:

1 Byte (B)

100 Bytes (B)

1,000 Bytes = 1 Kilo Byte (KB)

1,000,000 Bytes = 1,000 KB = 1 Mega Byte (MB)

1,000,000,000 Bytes = 1,000 MB = 1 Giga Byte (GB)

1,000,000,000,000 Bytes = 1,000 GB = 1 Tera Byte (TB)

1,000,000,000,000,000 Bytes = 1,000 TB = 1 Peta Byte (PB)

It is important to note, when you are referring to the computers Hard Disk (HD), Random Access Memory (RAM), or Network Connection, all the numbers are stored and displayed by the computer are in binary format, not decimal format.  This includes the size of files.  It just so happens a KB, that is 2¹⁰, is approximately equal to 1,000 in decimal notation (actually it is 1024) and a MB, 2²⁰ is approximately equal to 1,000,000 (actually 1,048,576). Although for our human heads, its generally easy to think in the simple powers of ten, just remember that these are not exact!