Units of Measure | CompTIA IT Fundamentals FC0-U61 | 1.5

In this video you will be learning about storage units, throughput units, and processing speeds.

Storage units measure the capacity of permanent storage, including magnetic, optical, and flash memory drives; read-only memory (ROM) and random-access memory (RAM aka temporary storage).  Storage units use two number systems: decimal powers of two and decimal powers of ten.

Storage Unit


A bit (short for binary digit) is the smallest unit of measurement used to quantify computer data.  It contains a single binary value (base 2) of 0 or 1.


The term bits (plural) refers to the size of the internal registers in a CPU (processor).  A nibble is equal to four bits. A 32-bit processor can process information in 32-bit-wide elements and can also access memory addresses up to 2^32 (4,294,967,296 or 4GB).  A 64-bit processor can process information in 64-bit-wide elements and can also access memory addresses up to 2^64 (18,446,744,073,709,600,000 or 18 ZB [zettabytes]).


A byte is a data measurement unit that contains eight bits, or a series of eight zeros and ones.  A single byte can be used to represent 2^8 or 256 different values.  Also, a single character in a plaintext file requires a byte to store it.  Multiples of byte are used by all larger units of measure.

Kilobyte (KB)

A kilobyte (abbreviated K or KB) is the smallest unit of measurement greater than a byte.  It precedes the megabyte, which contains 1,000,000 bytes. The kilobyte is 1,000 bytes when expressed in decimal powers of 10 and 1,024 bytes when expressed in decimal powers of 2.

Megabyte (MB)

A megabyte (MB) is equal to 1,000 kilobytes and precedes the gigabyte unit of measurement.  Depending on the device, the megabyte is either 1,048,576 bytes (1024 kilobytes using powers of 2) or 1,000,000 bytes (decimal, powers of 10).  RAM (system memory or cache memory) is often expressed using the powers of 2 decimal method, whereas the rated capacity of storage drives and media is expressed using the decimal measurements.  To calculate the binary MB value from a value in millions, divide the capacity in bytes by 1,048,576.

Megabytes Displayed on Property Sheet

Gigabyte (GB)

A gigabyte (GB) is equal to 1,000 megabytes and precedes the terabyte unit of measurement.  Depending upon the device, a gigabyte is either 1,073,741,824 (1024 megabytes in powers of 2) or 1,000,000,000 bytes (decimal, powers of 10).  To calculate the binary GB value from a value in billions, divide the capacity in bytes by 1,073,741,824.

Gigabytes Displayed on Property Sheet

Terabyte (TB)

A terabyte (TB) is equal to 1,000 gigabytes and precedes the petabyte unit of measurement.  A terabyte is either 1,099,511,627,776 bytes (1024 gigabytes using powers of 2) or 1,000,000,000,000 bytes (powers of 10).  Storage vendors generally measure their drives using powers of 10 capacities while operating systems use powers of 2 (binary) measurements.

Petabyte (PB)

A petabyte (PB) is equal to 1,000 terabytes.  Depending on the device, a petabyte is either 1,125,899,906,842,620 (1024 terabytes using powers of 2) or 1,000,000,000,000,000 bytes (decimal, powers of 10).  Petabyte-sized drive arrays are used in cloud storage & backup systems.

Capacity Comparison

Binary KB – PB Capacity in Bytes

Throughput Unit

Throughput units are used to measure the speed at which data is transferred between endpoints, such as from internet to a broadband modem, or from a hard drive to a computer.  Throughput units use powers of 10 (decimal) numbering systems.

Bits per Second (bps)

Bits per second (bps or bit/sec) is a common measure of data speed for computer modems and transmission carriers.  As the term implies, the speed in bps is equal to the number of bits transmitted or received each second. Also worth noting, bps was used mainly to measure the speed of early dial-up (analog) modems.

Kilobit per Second (Kbps)

One kilobit per second (Kbps) equals 1000bps.  Kbps is primarily used to measure the speeds of low-performance DSL internet connections (256 – 768Kbps).

Megabit per Second (Mbps)

One megabit per second (Mbps) equals 1000Kbps.  Mbps is widely used to measure the speeds of high-speed and broadband internet connections, LAN connections, & I/O devices such as USB 1.1, USB 2.0 & FireWire.

Gigabit per Second (Gbps)

One gigabit per second (Gbps) equals 1000Mbps.  Gbps measurements are primarily used to express the speeds of very fast internet and LAN connections (Giga ethernet and 10G ethernet) and the speed of high-performance device interconnects such as USB 3.1 Gen 1 (5Gbps), USB 3.1 Gen 2 (10Gbps), and SATA Revision 3 (6Gbps).

Terabyte per Second (Tbps)

One terabyte per second (Tbps) equals 1000Gbps.  Tbps is used primarily to measure the speeds of internet connections between countries and regions.

Processing Speed

Processing speed (aka clock speed) is the speed at which a microprocessor executes instructions.  That is, the number of cycles a processor can perform per second. The processing speed is controlled by a crystal oscillator clock chip on the motherboard.  Each combination of a pulse and rest is a clock cycle.

A Clock Cycle

Megahertz (MHz)

A megahertz (MHz) is equal to 1,000,000 cycles per second or 1,000 kilohertz.  MHz is also used to measure the I/O bus clock rate used by memory modules.

Gigahertz (GHz)

A gigahertz (GHz) is equal to 1,000,000,000 cycles per second or 1,000MHz.  Almost all processors used in PCs manufactured in the last 15 years have run at speeds exceeding 1GHz.