A bit represents one binary state; a byte is eight bits. Decimal prefixes use powers of 1,000, so 1 GB is 1,000,000,000 bytes. Binary prefixes use powers of 1,024, so 1 GiB is 1,073,741,824 bytes. A storage label and an operating-system display can therefore show different numbers even before formatting, system files, recovery areas or reserved capacity are considered.
Start with the unit, then the prefix
| Expression | Exact relationship | Typical context |
|---|---|---|
| 1 byte (B) | 8 bits | File size and storage capacity |
| 1 kilobyte (kB) | 1,000 bytes | Decimal SI-based capacity or data-rate contexts |
| 1 kibibyte (KiB) | 1,024 bytes | Binary IEC-based memory or software reporting |
| 1 gigabyte (GB) | 1,000,000,000 bytes | Drive and transfer capacity using decimal notation |
| 1 gibibyte (GiB) | 1,073,741,824 bytes | Explicit binary capacity |
| Mb/s | megabits per second | Network link or transfer rate; divide by eight for a theoretical MB/s before overhead |
What binary representation does
Binary notation uses two symbols, commonly 0 and 1. Digital systems can map physical states into those logical values and combine bits to represent numbers, text, instructions, colour, sound and many other forms of information.
The representation is not the meaning by itself. A sequence of bits needs an agreed encoding, file format, instruction set or protocol before software knows how to interpret it.
Why usable or displayed capacity varies
- The label and display may use decimal and binary units
- Formatting creates file-system structures
- Operating systems, recovery partitions and applications occupy space
- Storage devices may reserve capacity for management and reliability
- A network rate is not a guaranteed file-copy rate because protocol, signal, device and storage overhead remain
Sources and further reading
Technical statements were reviewed against these references. External pages may change after our review date.
- Definitions of the SI units: The binary prefixes — National Institute of Standards and Technology
- The International System of Units: SI prefixes — Bureau International des Poids et Mesures