What is a Gigabyte (GB)?
A gigabyte (GB) is a decimal (base-10) unit of digital storage defined by the International System of Units (SI):
Usage:
- Storage devices (HDDs, SSDs) and internet service providers use GB to denote capacity or data transfer rates.
What is a Gibibyte (GiB)?
A gibibyte (GiB) is a binary (base-2) unit standardized by the International Electrotechnical Commission (IEC):
Usage:
- Operating systems like Windows use GiB but often mislabel it as “GB,” causing confusion.
- Correction: macOS typically displays storage in true SI units (GB), not GiB.
Key differences: SI (Base-10) vs. IEC (Base-2)
SI System (Decimal)
- Units: GB (gigabyte), TB (terabyte).
- Formula:
IEC system (binary)
- Units: GiB (gibibyte), TiB (tebibyte).
- Formula:
Difference:
1 \text{ GiB} \approx 1.074 \text{ GB} \quad (\text{~7.37% larger than 1 GB}).Conversion formulas
GB to Bits (SI)
- Convert GB to bytes:
- Convert bytes to bits (1 byte = 8 bits):
General Formula:
GiB to Bits (IEC)
- Convert GiB to bytes:
- Convert bytes to bits:
General Formula:
Practical examples
Example 1: Converting 5 GB to Bits (SI)
Example 2: Converting 5 GiB to Bits (IEC)
Example 3: Internet Data Plan
A 100 GB monthly plan equals:
Why storage shows less capacity than advertised
A “1 TB” drive (SI units):
In IEC units:
Result: Windows displays ~931 GiB for a “1 TB” drive.
Common mistakes & clarifications
- GB vs. GiB:
- Storage marketed in GB (SI) but often displayed in GiB (IEC) by OS.
- Bits vs. Bytes:
- Network speeds (e.g., 100 Mbps) use bits; storage uses bytes.
- OS-Specific Behavior:
- Windows: Uses GiB but labels as “GB.”
- macOS: Uses true GB (SI) for storage.
Historical context
- Pre-1998: SI prefixes (kilo, mega) were ambiguously applied to binary units.
- 1998: IEC introduced binary prefixes (kibi, mebi, gibi) to resolve confusion.
Frequently asked questions
How many bits are in 1 GB?
In the SI system:
Why does my 1 TB drive show only 931 GiB?
The drive uses SI units (1 TB = 10^{12} bytes), but Windows converts to IEC:
How to convert 3.5 GiB to bits?
Using the IEC formula:
What’s the practical difference between GB and GiB?
- 1 GB = 1,000,000,000 bytes (SI).
- 1 GiB = 1,073,741,824 bytes (IEC).
Difference: ~7.37%.
Why are internet speeds measured in bits?
Bits per second (bps) standardize data transmission rates. Example:
Notes
- Storage devices: Marketed in SI units (GB/TB).
- Memory (RAM): Often uses IEC (GiB) but mislabeled as “GB.”
- Data transmission: Always measured in bits (e.g., Mbps).