KB vs KiB vs MB vs MiB
Differences, use cases, and when to use each
KB (kilobyte) officially means 1,000 bytes (SI prefix). KiB (kibibyte) means 1,024 bytes (binary prefix). MB means 1,000,000 bytes; MiB means 1,048,576 bytes. Storage manufacturers use SI (KB); operating systems use binary (KiB) but label it KB, causing the '1TB hard drive appears as 931 GB' confusion.
Quick Comparison
| Feature | KB vs KiB | MB vs MiB |
|---|---|---|
| KB Definition | 1,000 bytes (SI standard) | 1,024 bytes (traditional binary) |
| MB Definition | 1,000,000 bytes | 1,048,576 bytes |
| Used By | Storage manufacturers, SI standard | Operating systems (mislabeled) |
| Confusion | — | Windows shows GiB but labels it GB |
| Standard | IEC 80000-13 (KiB, MiB, GiB) | Historical computing convention |
When to Use Each
When to Use KB vs KiB
Use SI units (KB = 1,000 bytes) when following the IEC standard or communicating storage capacity in hard drives, SSDs, and flash storage per manufacturer specs.
When to Use MB vs MiB
Use binary units (KiB = 1,024 bytes) when discussing RAM sizes, file system blocks, and the values that operating systems actually compute, using the correct KiB/MiB/GiB labels.
Pros & Cons
KB vs KiB
MB vs MiB
Verdict
The confusion is real and widespread. A 1 TB (SI) drive appears as ~931 GiB in your OS. Use KiB/MiB/GiB labels when precision matters; understand that OS 'GB' actually means GiB.