Data Storage Units: Bytes, KB, MB, GB (and KiB vs KB)
Digital storage is measured in bits and bytes, but there are two systems that both get called “kilobyte” — a decimal one based on 1,000 and a binary one based on 1,024. That mismatch is why a “1 TB” drive shows up as about 931 GB in your operating system. Here's how both work.
Updated 2026-07-06
Decimal units (SI, powers of 1,000)
Used by storage manufacturers, networking (Mbps), and most consumer specs. Each step up multiplies by 1,000.
| Unit | Equals | Notes |
|---|---|---|
| Bit (b) | 1 bit | A single 0 or 1 — the smallest unit |
| Byte (B) | 8 bits | Enough to store one character |
| Kilobyte (KB) | 1,000 bytes | 10³ bytes |
| Megabyte (MB) | 1,000 KB | 10⁶ bytes |
| Gigabyte (GB) | 1,000 MB | 10⁹ bytes |
| Terabyte (TB) | 1,000 GB | 10¹² bytes |
| Petabyte (PB) | 1,000 TB | 10¹⁵ bytes |
Binary units (IEC, powers of 1,024)
Used by operating systems and memory (RAM). The -bi- names (kibi, mebi, gibi) exist specifically to remove the ambiguity, though many systems still label these as KB/MB/GB.
| Unit | Equals | Notes |
|---|---|---|
| Kibibyte (KiB) | 1,024 bytes | 2¹⁰ bytes |
| Mebibyte (MiB) | 1,024 KiB | 2²⁰ bytes (≈ 1.049 MB) |
| Gibibyte (GiB) | 1,024 MiB | 2³⁰ bytes (≈ 1.074 GB) |
| Tebibyte (TiB) | 1,024 GiB | 2⁴⁰ bytes (≈ 1.100 TB) |
Bits vs. bytes: the networking gotcha
Storage is measured in bytes (capital B), but network speeds are measured in bits(lowercase b). Since a byte is 8 bits, a “100 Mbps” connection downloads at roughly 12.5 MB/s, not 100. Divide the advertised speed by 8 to estimate the real download rate. To convert between many other units, the unit converter handles data sizes too.
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