A gigabyte (derived from the SI prefix giga-) is a unit of information or computer storage meaning either exactly 1 billion bytes (10003 or 109) or approximately 1.07 billion bytes (10243).
The usage of the word "gigabyte" is ambiguous, depending on the context. When referring to RAM sizes and file sizes, it traditionally has a binary definition, of 10243 bytes. For other uses, it means exactly 10003 bytes. In order to address this confusion, currently the International Electrotechnical Commission (IEC) promotes the use of the term "gibibyte" for the binary definition. This position is endorsed by other standards organizations including the Institute of Electrical and Electronics Engineers (IEEE), the International Committee for Weights and Measures (CPIM) and the National Institute of Standards and Technology (NIST).
It is commonly abbreviated GB or Gbyte (cf. Gb, which is used for a gigabit).
Gigabytes vs. gigabits
In conventional modern usage, a byte is 8 bits. One gigabyte is equivalent to eight gigabits.
In computer networking, however, the conventional SI units are followed. Manufacturers of networking equipment always use 1000-bit kilobits as their basic unit of measurement.
| Abbreviation | No. of bytes | Usage | |
|---|---|---|---|
| gigabytes | GB (Note: uppercase "B") | 10003 | Computer storage (e.g., 500 GB hard disk) |
| gigabytes | GB (Note: uppercase "B") | 10243 | Computer memory (e.g., 4 GB RAM) |
| gibibytes | GiB (Note: uppercase "B") | 10243 | Computer storage (e.g., 34 GiB file) |
| gigabit | Gbit or Gb | 125*10002 | Network throughput (eg 1 Gbit/s data transfer rate) |
