File & Storage Size

Files and digital storage devices store data using binary code. What this means is that information is actually stored through a series of 0s and 1s, and this series of 0s and 1s conveys all the digital information we are used to seeing today. Each 0 or 1 is referred to as a bit, and eight bits equals one byte.

The byte is the most basic unit of storage for files and digital storage. If all you want to do is measure a file or storage device in bytes, then there is no dispute about measuring it. However, if you want to shorten this measurement, things can become tricky.

For instance, let's take a look at a file that is 1 kilobyte. How many bytes is this file? Traditionally, the prefix kilo meant 1,000 of something. So, one might assume that a kilobyte is 1,000 bytes. However, when computers look at files and device storage, they use groups of 1,024. So, for a computer, a kilobyte would be a 1,024 bytes. In December 1998, the International Electrotechnical Commission (IEC) approved new prefixes to reflect this reality. The traditional prefixes along with the new prefixes are shown below [1]:

Bytes Abbreviation Pronunciation
1,000 KB kilobyte
1,024 KiB kibibyte
1,000,000 MB megabyte
1,048,576 MiB mebibyte
1,000,000,000 GB gigabyte
1,073,741,824 GiB gibibyte
1,000,000,000,000 TB terabyte
1,099,511,627,776 TiB tebibytes

It is important to be aware of this discrepancy since storage manufacturers may use the traditional way of measuring bytes rather than the 1,024 way of measuring bytes. For example, while hard drive manufacturers will typically measure a 500,000,000,000 byte hard drive as 500 GB, a computer will typically report that the drive is 465 GB.



1. Definitions of the SI units: The binary prefixes. ©1997 the Institute of Electrical and Electronics Engineers.