Petabyte (PB) - Unit Information & Conversion

Definition

A petabyte (PB) is a multiple of the byte unit for digital information storage. The prefix peta- (symbol P) is defined in the International System of Units (SI) as a multiplier of 1015 (1 quadrillion, or 1 followed by 15 zeros). Therefore, 1 petabyte = 1,000,000,000,000,000 bytes. This is equivalent to 1,000 terabytes (TB) or 1,000,000 gigabytes (GB). The petabyte is distinct from the pebibyte (PiB), which uses the binary prefix 'pebi-' established by the International Electrotechnical Commission (IEC) and equals 250 bytes.

History

The prefix 'peta-' originates from the Greek word "pente," meaning five (as 1015 = 10005), and was officially adopted as an SI prefix in 1975. In computing and data storage, the term 'petabyte' became necessary as data volumes grew exponentially beyond the terabyte scale in the late 20th and early 21st centuries. Initially, like other SI prefixes (kilo-, mega-, giga-, tera-), 'peta-' was sometimes ambiguously used by some to refer to the nearest power of 2 (250). However, the formal adoption of binary prefixes like 'pebi-' (Pi) by the IEC in 1998 aimed to resolve this confusion, clarifying that petabyte (PB) should strictly refer to 1015 bytes, while pebibyte (PiB) refers to 250 bytes. Despite standardization, the term PB is still sometimes used loosely in casual contexts, but in technical specifications and marketing, PB almost always means 1015 bytes.

Common Uses

Petabytes are used to quantify extremely large amounts of digital storage and data:

• Capacity of large-scale data centers, cloud storage platforms (e.g., Google Drive, AWS S3, Azure Blob Storage), and enterprise storage systems.
• Big data analytics, involving the processing and storage of vast datasets for scientific research (like genomics, particle physics, astronomy), business intelligence, and machine learning model training.
• National digital archives, large media libraries, and corporate data repositories storing historical records, high-resolution multimedia content, or extensive backups.
• High-performance computing (HPC) environments managing massive simulation outputs or experimental data collections.
• Large-scale video surveillance systems storing continuous high-resolution footage from numerous cameras.
• Quantifying the total amount of data generated globally or traversing major internet backbones over periods.

Unit FAQs

How many bytes are in a petabyte (PB)?

There are exactly 1,000,000,000,000,000 bytes (one quadrillion bytes, or 1015 bytes) in 1 petabyte (PB), according to the standard SI definition of the prefix 'peta-'.

How many terabytes (TB) are in a petabyte (PB)?

There are 1,000 terabytes (TB) in 1 petabyte (PB). This follows the SI prefixes where each prefix increases by a factor of 1,000: 1 PB = 1015 bytes and 1 TB = 1012 bytes. Therefore, 1 PB / 1 TB = 1015 / 1012 = 103 = 1,000.

What is the difference between a petabyte (PB) and a pebibyte (PiB)?

• A petabyte (PB) uses the decimal SI prefix 'peta-' and equals 1015 bytes (1,000,000,000,000,000 bytes). It is commonly used in storage marketing and cloud capacity definitions.
• A pebibyte (PiB) uses the binary IEC prefix 'pebi-' and equals 250 bytes (1,125,899,906,842,624 bytes). It is used for precise measurement in technical contexts where powers of 2 are relevant (like OS reporting or memory architecture).

A pebibyte is approximately 12.6% larger than a petabyte (1 PiB ≈ 1.126 PB).

What is the difference between a petabyte (PB) and a petabit (Pb)?

• A petabyte (PB) measures data storage capacity in bytes and equals 1015 bytes.
• A petabit (Pb) measures data quantity or data transfer speed in bits and equals 1015 bits.

Assuming the standard definition of 1 byte = 8 bits, 1 petabyte (PB) is equal to 8 petabits (Pb). Calculation: 1 PB = 1015 bytes = 1015 * 8 bits = 8 * 1015 bits = 8 Pb. Therefore, a petabyte represents 8 times more data storage capacity than the equivalent number of petabits.

Why is PB often used in marketing instead of PiB?

Storage manufacturers typically market drive and system capacities using the decimal prefix petabyte (PB) because 1015 bytes yields a larger, rounder number compared to the equivalent value expressed using the binary prefix pebibyte (PiB) (which is 250 bytes). For instance, a storage system containing exactly 1,000,000,000,000,000 bytes is advertised as 1 PB. If measured in pebibytes, this same physical capacity would be approximately 0.888 PiB (since 1015 / 250 ≈ 0.888). Using PB allows manufacturers to present higher capacity figures, which is advantageous for marketing. This often leads to discrepancies where users see a marketed capacity in PB (or TB, GB) but their operating system reports a lower number when using binary calculations (often labeled GiB/TiB/PiB, or sometimes confusingly still labeled GB/TB/PB).