Data units explained: KB, MB, GB and TB
Two counting systems and a bit-vs-byte mix-up cause most data-size confusion. Here’s the whole picture, clearly.
There are two systems. Decimal (SI): each step is ×1000 (kB, MB, GB, TB). Binary (IEC): each step is ×1024 (KiB, MiB, GiB, TiB). And remember: 8 bits = 1 byte.
Decimal vs binary
Historically, “KB/MB/GB” were used loosely for both 1000- and 1024-based values, which is exactly why a drive’s size can look different in different places. The IEC introduced separate binary names (KiB, MiB, GiB) to remove the ambiguity.
| Unit | Equals | Bytes |
|---|---|---|
| 1 kilobyte (kB) | 1,000 bytes | 10³ |
| 1 megabyte (MB) | 1,000 kB | 10⁶ |
| 1 gigabyte (GB) | 1,000 MB | 10⁹ |
| 1 terabyte (TB) | 1,000 GB | 10¹² |
| Unit | Equals | Bytes |
|---|---|---|
| 1 kibibyte (KiB) | 1,024 bytes | 2¹⁰ |
| 1 mebibyte (MiB) | 1,024 KiB | 2²⁰ |
| 1 gibibyte (GiB) | 1,024 MiB | 2³⁰ |
| 1 tebibyte (TiB) | 1,024 GiB | 2⁴⁰ |
Bits vs bytes
A bit is a single 1 or 0; a byte is eight bits. Storage is measured in bytes (with a capital B: MB, GB). Network and internet speeds are measured in bits (lower-case b: Mbps, Gbps). To convert a connection speed to a download rate, divide by 8:
Worked example
You buy a “2 TB” drive. That’s 2,000,000,000,000 bytes (decimal). Your operating system may report it in binary: 2,000,000,000,000 ÷ 1024³ ≈ 1,862 GiB (about 1.82 TiB). Same drive, two labels.