Data Storage Guide: Bits, Bytes, KB, MB, GB, TB & Beyond
Digital storage units can be confusing — especially the difference between binary and decimal systems. Here's everything you need to know about data sizes.
Data Storage Units (Decimal / SI)
| Unit | Symbol | Bytes | Example |
|---|---|---|---|
| Bit | b | 1/8 byte | Single 0 or 1 |
| Byte | B | 1 | Single character |
| Kilobyte | KB | 1,000 | Short text file |
| Megabyte | MB | 1,000,000 | MP3 song (~4 MB) |
| Gigabyte | GB | 1,000,000,000 | Movie (~1–2 GB) |
| Terabyte | TB | 1,000,000,000,000 | Hard drive |
| Petabyte | PB | 10¹⁵ | Data centre |
Frequently Asked Questions
How many bytes in a kilobyte?
In the decimal (SI) system: 1 KB = 1,000 bytes. In the binary system: 1 KiB (kibibyte) = 1,024 bytes. Operating systems and storage manufacturers often use different conventions. Hard drive manufacturers use 1 KB = 1,000 bytes, but Windows shows drives slightly smaller because it uses 1 KB = 1,024 bytes.
How many GB in a TB?
1 TB (terabyte) = 1,000 GB (decimal) or 1,024 GiB (binary). For consumer storage like hard drives and SSDs, 1 TB = 1,000 GB in marketing terms. This is why a '1 TB drive' shows as about 931 GB in Windows (which uses binary).
What is a bit vs a byte?
A bit is the smallest unit of digital data — a 0 or 1. A byte = 8 bits. Network speeds are measured in bits per second (Mbps, Gbps). File sizes are measured in bytes (KB, MB, GB). A 100 Mbps internet connection downloads at 12.5 MB/s (100 ÷ 8).
What is the largest data storage unit?
Standard progression: Byte → KB → MB → GB → TB → PB (petabyte) → EB (exabyte) → ZB (zettabyte) → YB (yottabyte). 1 yottabyte = 10²⁴ bytes. The entire internet is estimated to be a few zettabytes of data.
Why does my 256 GB phone show less available storage?
The phone manufacturer uses decimal GB (1 GB = 1,000,000,000 bytes), but iOS and Android display in binary GiB (1 GiB = 1,073,741,824 bytes). 256 GB ÷ 1.0737 ≈ 238 GiB. The remaining difference is the OS, pre-installed apps, and file system overhead.
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