EMZETT.Storage units: from kilobyte to zettabyte
In short: Data amounts are given in multiples of the byte: kilobyte, megabyte, gigabyte, terabyte, petabyte, exabyte, zettabyte, yottabyte. Each step is 1000 times (SI) or 1024 times (binary) the previous one.
In more detail: A byte is 8 bits and can store a letter. Everything larger consists of prefixes from the International System of Units. The difference between decimal (prefix 1000) and binary (1024) matters.
In Depth
| Unit | Symbol | Decimal (SI) | Binary (IEC) | Example |
|---|---|---|---|---|
| Byte | B | 1 | 1 | one character |
| Kilobyte | KB | 10³ = 1,000 | KiB = 2¹⁰ = 1,024 | short text |
| Megabyte | MB | 10⁶ | MiB = 2²⁰ | photo, MP3 song |
| Gigabyte | GB | 10⁹ | GiB = 2³⁰ | HD movie |
| Terabyte | TB | 10¹² | TiB = 2⁴⁰ | hard drive |
| Petabyte | PB | 10¹⁵ | PiB = 2⁵⁰ | data center, Facebook photos per day |
| Exabyte | EB | 10¹⁸ | EiB = 2⁶⁰ | worldwide internet traffic per day |
| Zettabyte | ZB | 10²¹ | ZiB = 2⁷⁰ | worldwide annual data volume (~100+ ZB) |
| Yottabyte | YB | 10²⁴ | YiB = 2⁸⁰ | exceeds current total storage |
- Smaller than a byte: Bit (1/8 byte), nibble (4 bits).
- Pico-, femto-: “Pico” stands for 10⁻¹², but there is no “picobyte” as a data amount since nothing is smaller than a bit. Pico is used for time (picosecond), length and current (picoampere). Whoever reads “picobyte” in exercises usually means petabyte (PB).
- Why does the 1 TB disk show only 931 GB? Manufacturers calculate decimally (10¹² bytes), Windows shows binary (GiB, but labeled “GB”): 10¹² / 1,073,741,824 ≈ 931.
- Data transfer: Networks are given in bits per second (Mbit/s). 100 Mbit/s are 12.5 MB/s.
- Converting: Byte = bit ÷ 8. Between steps multiply/divide by 1000 (or 1024).
- Example: A 4 GB DVD holds about 4,000 MB. The 1.44 MB floppy hardly held a photo.
See also: Units and conversion (SI, byte, temperature), Byte, Bits