Understanding digital data units is essential in everyday life: hard drive capacity, file size, internet connection speed, photo or video size. Confusion between KB/MB/GB/TB is common, especially since the introduction of binary units (kibibytes, mebibytes).
Data units use decimal prefix (1 KB = 1,000 bytes) or binary (1 KiB = 1,024 bytes) depending on context. Hard drive manufacturers use base 10 (a 1 TB drive = 1,000,000,000,000 bytes), while operating systems use base 2 (the same drive shows ~931 GiB). This difference explains why a 1 TB drive appears smaller once formatted.
📐 Formula
1 KB = 1,000 bytes | 1 MB = 1,000 KB | 1 GB = 1,000 MB | 1 TB = 1,000 GB (decimal)
1 KiB = 1,024 bytes | 1 MiB = 1,024 KiB | 1 GiB = 1,024 MiB (binary)
📊 Reference table
| Unit | Abbreviation | Value in bytes (decimal) | Value in bytes (binary) |
|---|---|---|---|
| kilobyte | KB | 1,000 | 1,024 (KiB) |
| megabyte | MB | 1,000,000 | 1,048,576 (MiB) |
| gigabyte | GB | 1,000,000,000 | 1,073,741,824 (GiB) |
| terabyte | TB | 1,000,000,000,000 | 1,099,511,627,776 (TiB) |
| petabyte | PB | 1,000,000,000,000,000 | ~1.13 × 10¹⁵ (PiB) |
💡 Practical examples
Example 1: smartphone photo file size
A 12MP photo weighs about 3–5 MB. 1 GB of storage can hold 200–333 photos. A 1-minute Full HD video ≈ 150–300 MB depending on compression.
Example 2: 1 TB hard drive shown in GB
1 TB (decimal) = 1,000 GB. But Windows shows GiB: 1,000,000,000,000 / 1,073,741,824 ≈ 931 GiB. That's why a '1 TB' SSD shows '931 GB' in Explorer.
Example 3: internet speed and download time
A 1 GB file on a 100 Mbps connection: time = (1,000 × 8) / 100 = 80 seconds. Note: internet speeds are in bits, file sizes in bytes — divide Mbps by 8 to get MB/s!