Computer Memory Units Explained

Computer memory has grown exponentially in the past three decades, and each generation of memory brings with it a new level of memory units and new terms to learn. Let's take a look at these units.

Building blocks

Bits and bytes are the basic building blocks of memory. "Bit" stands for binary digit. A bit is a one or a zero, on or off, which is how all computer information is stored. A byte is made up of eight bits. Eight bits, or a byte, was the original amount of information needed to encode a character of text. The number was later standardized as computer hardware changed.

For technical reasons, computer memory capacity is expressed in multiples of a power of two. The metric prefixes were then applied to those multiples to provide an easy way to express the very large numbers of bits and bytes.

SI prefixes

Computer memory uses a portion of the International System of Units (SI) prefixes for multiples of the base unit, a byte. The prefixes are not truly metric, however, because a byte is eight bits, a kilobyte is 1024 bytes.

Memory Prefix


Kilo (Kilobyte, KB)

1,024 Bytes

Mega (Megabyte, MB)

1,024 Kilobytes

Giga (Gigabyte, GB)

1,024 Megabytes

Tera (Terabyte, TB)

1,024 Gigabytes

Peta (Petabyte, PB)

1,024 Terabytes

Memory units

Computers use memory in random access memory (RAM), which stores information temporarily and in storage drives, which permanently store data. RAM allows your computer to switch between programs and have large files ready to view.

Depending on what you use your computer for, you generally want as much memory as your computer will hold. The manufacturer and model of your computer determines what kind and how much memory your computer came with and the maximum amount and speed it can accommodate. Use the Crucial® Advisor™ tool or System Scanner tool to find compatible memory. To learn more about how much memory you should have, read here.

Crucial SSD and RAM memory modules

Storage drives; hard disk drives and solid state drives, use the same memory terms when describing the capacity of the drive. As files  with videos and very large photographs get larger, larger drive capacities are needed, as well. Currently, solid state drives are sold in a number of different gigabyte and terabyte capacities. As with RAM, you can use the Crucial® Advisor™ tool or System Scanner tool to find an SSD that's compatible with your system.