Bits and Bytes
A bit is a single binary digit (0 or 1). A byte is 8 bits. Storage capacity and file sizes are counted in bytes, symbol B (capital). The bit has the symbol bit, and is often abbreviated b (lowercase), so MB means megabytes and Mb means megabits — a factor of 8 apart.
Decimal SI Units: kB, MB, GB, TB
The SI prefixes kilo (k), mega (M), giga (G) and tera (T) mean 10³, 10⁶, 10⁹ and 10¹², exactly as in kilometre or gigawatt. The kilo prefix is a lowercase k. The SI Brochure states that these prefixes refer strictly to powers of 10 and should not be used for powers of 2 (BIPM SI Brochure, 9th edition (2019)). Storage manufacturers commonly label capacity with these decimal units.
| Unit | Symbol | Bytes |
|---|---|---|
| kilobyte | kB | 1,000 |
| megabyte | MB | 1,000,000 |
| gigabyte | GB | 1,000,000,000 |
| terabyte | TB | 1,000,000,000,000 |
Try the Calculator
Use our free Gigabytes to Gibibytes converter for instant, accurate results.
💾Convert GB → GiBBinary IEC Units: KiB, MiB, GiB, TiB
For powers of 1,024, the IEC defined separate prefixes — kibi (Ki), mebi (Mi), gibi (Gi), tebi (Ti) — first in IEC 60027-2 (1998), now in IEC 80000-13 (NIST: Prefixes for binary multiples). Note the capital K in KiB. The correct name for 1,073,741,824 bytes is gibibyte (GiB), not "binary gigabyte".
| Unit | Symbol | Bytes |
|---|---|---|
| kibibyte | KiB | 1,024 (2¹⁰) |
| mebibyte | MiB | 1,048,576 (2²⁰) |
| gibibyte | GiB | 1,073,741,824 (2³⁰) |
| tebibyte | TiB | 1,099,511,627,776 (2⁴⁰) |
Why the Displayed Number Is Smaller
Divide a decimal byte count by a binary unit and the number shrinks, because each binary unit is larger:
1 GB = 1,000,000,000 ÷ 1,073,741,824 ≈ 0.9313 GiB
1 TB = 1,000,000,000,000 ÷ 1,099,511,627,776 ≈ 0.9095 TiB
So a drive sold as 1 TB holds 1,000,000,000,000 bytes, which is about 931.3 GiB. The byte count has not changed; only the unit describing it has. The gap grows with each step: about 2.4% at kilo, 4.9% at mega, 7.4% at giga and 10.0% at tera.
Labels can mislead
🧮Quick Calculator
1 GB = 0 GiB
Symbol and Capitalisation Traps
- GB ≠ GiB and TB ≠ TiB: decimal and binary units are different sizes. - MB ≠ Mb: capital B is byte, lowercase b is bit. - kB, not KB, for 1,000 bytes: the SI prefix is lowercase k; KiB is the binary unit. - "1 GB = 1,024 MB" is wrong under both systems: 1 GB = 1,000 MB, and 1 GiB = 1,024 MiB.
When a figure matters, state the unit explicitly or give the raw byte count.
Converter and Sources
Use the gigabytes to gibibytes converter for exact figures. Definitions on this page follow the BIPM SI Brochure, 9th edition (2019), IEC 80000-13 and NIST: Prefixes for binary multiples. See our methodology for how we check unit definitions.