Bits, Bytes and Megabytes: Understanding Data Sizes
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Data units describe how much information a file, device or connection handles. Understanding the labels helps you compare storage space and download speeds.
Bits and Bytes
A bit is a binary digit. A byte contains eight bits. File sizes are commonly expressed in bytes, while connection speeds are often expressed in bits per second.
For example, 80 megabits per second corresponds to 10 megabytes per second before allowing for transfer overhead and real-world conditions.
Decimal Data Units
| Unit | Symbol | Number of Bytes |
|---|---|---|
| Kilobyte | kB | 1,000 |
| Megabyte | MB | 1,000,000 |
| Gigabyte | GB | 1,000,000,000 |
| Terabyte | TB | 10¹² |
| Petabyte | PB | 10¹⁵ |
| Exabyte | EB | 10¹⁸ |
| Zettabyte | ZB | 10²¹ |
| Yottabyte | YB | 10²⁴ |
Binary Units Are Different
A kibibyte (KiB) contains 1,024 bytes. A mebibyte (MiB) contains 1,048,576 bytes. These binary units use powers of two rather than powers of ten.
Some software uses familiar labels such as MB while calculating with binary quantities. Check the definition when comparing an advertised capacity with the figure displayed by your device.
Tip: Notice the letter case: **Mb/s** means megabits per second, while **MB/s** means megabytes per second. They are not interchangeable.
