Data storage units (KB MB GB TB)
Drive makers usually count in decimal (1 GB = 1000 MB), while many OS tools show binary units as KiB/MiB/GiB (1 GiB = 1024 MiB) — which is why a “1 TB” drive seems smaller than advertised.
| Unit | Equals | Notes |
|---|---|---|
| 1 byte (B) | 8 bits | Basic addressable unit |
| 1 Kb (kilobit) | 1000 bits | Often network rates (kbps) |
| 1 KB (kilobyte, decimal) | 1000 bytes | SI-style |
| 1 KiB (kibibyte) | 1024 bytes | IEC binary |
| 1 MB | 1000 KB ≈ 10^6 B | Decimal mega |
| 1 MiB | 1024 KiB | Binary mebi |
| 1 GB | 1000 MB ≈ 10^9 B | Disk marketing often |
| 1 GiB | 1024 MiB | OS “GB” sometimes means this |
| 1 TB | 1000 GB ≈ 10^12 B | Decimal tera |
| 1 TiB | 1024 GiB | Binary tebi |
| 1 PB | 1000 TB | Decimal peta |
Notes
- Capital B usually means byte; lowercase b means bit (Mbps ≠ MBps).
- Why a “1 TB” drive shows ~0.91 TiB in some tools: 1000³ vs 1024³.
Frequently asked questions
- How many MB in a GB?
- In decimal (SI) units, 1 GB = 1000 MB. Some operating systems use binary units instead, where 1 GiB = 1024 MiB.
- What is the difference between KB and KiB?
- KB is the decimal kilobyte (1000 bytes), while KiB is the binary kibibyte (1024 bytes) defined by the IEC.
- Why does my 1 TB drive show only about 931 GB?
- Drive makers count 1 TB as 1000⁴ bytes, but some tools use binary units, so the same drive reads as roughly 0.91 TiB (≈931 GiB).