File Size Units Explained: KB, MB, GB, TB
File sizes are measured in bytes and scaled up using prefixes. Understanding these units helps you know how big your files really are — and why "1 GB" can mean different things on different systems.
📊 File Size Units Conversion Table
| Unit | Symbol | Decimal (SI) | Binary (IEC) | Short Form |
|---|---|---|---|---|
| Byte | B | 1 byte | 1 byte | B |
| Kilobyte | KB | 1,000 bytes | 1,024 bytes | KB / KiB |
| Megabyte | MB | 1,000,000 bytes | 1,048,576 bytes | MB / MiB |
| Gigabyte | GB | 1,000,000,000 bytes | 1,073,741,824 bytes | GB / GiB |
| Terabyte | TB | 1,000,000,000,000 bytes | 1,099,511,627,776 bytes | TB / TiB |
| Petabyte | PB | 10¹⁵ bytes | 2⁵⁰ bytes | PB / PiB |
⚖️ Binary vs Decimal — Why "1 GB" Is Confusing
Hard drive manufacturers use decimal (1 GB = 1,000,000,000 bytes) to make their drives seem larger. Operating systems use binary (1 GB = 1,073,741,824 bytes), which is why a "1 TB" hard drive shows as ~931 GB in Windows.
Storage manufacturers
1 GB = 1,000 MB
Decimal (SI)
Windows / Linux OS
1 GB = 1,024 MB
Binary (IEC)
📁 Real-World File Sizes
Plain text file (1 page)~4 KB
Word document (.docx)25–500 KB
PDF document (text)100 KB – 5 MB
JPEG photo (smartphone)2–8 MB
PNG screenshot (1080p)500 KB – 3 MB
WebP image50–300 KB
MP3 song (4 minutes)~5 MB at 160kbps
MP4 video (1 minute, 1080p)~150–500 MB
Blu-ray movie (2 hours)~25–50 GB