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Q: What units of measurement are used for data storage?

A: The smallest unit of measurement used for measuring data is a bit. A single bit can have a value of either 0 or 1. It may contain a binary value (such as On/Off or True/False), but nothing more. Therefore, a byte, or eight bits, is used as the fundamental unit of measurement for data. A byte can store 28 or 256 different values, which is sufficient to represent standard ASCII characters, such as letters, numbers and symbols.

Since most files contain thousands of bytes, file sizes are often measured in kilobytes. Larger files, such as images, videos, and audio files, contain millions of bytes and therefore are measured in megabytes. Modern storage devices can store thousands of these files, which is why storage capacity is typically measured in gigabytes or even terabytes. Larger units of measurement are usually reserved for measuring the sum of multiple storage devices or the capacity of large data storage networks.

Below is a list of all the standard units of measurement used for data storage, from the smallest to the largest.

UnitValueSize
bit (b)0 or 11/8 of a byte
byte (B)8 bits1 byte
kilobyte (KB)10001 bytes1,000 bytes
megabyte (MB)10002 bytes1,000,000 bytes
gigabyte (GB)10003 bytes1,000,000,000 bytes
terabyte (TB)10004 bytes1,000,000,000,000 bytes
petabyte (PB)10005 bytes1,000,000,000,000,000 bytes
exabyte (EB)10006 bytes1,000,000,000,000,000,000 bytes
zettabyte (ZB)10007 bytes1,000,000,000,000,000,000,000 bytes
yottabyte (YB)10008 bytes1,000,000,000,000,000,000,000,000 bytes

NOTE: A lowercase "b" is used as an abbreviation for bits, while an uppercase "B" represents bytes. This is an important distinction, since a byte is 8x as large as a bit.

For example, 100 KB (kilobytes) = 800 Kb (kilobits).

Updated: October 13, 2012