Free File Size Converter
Quickly convert between all common file size units. Supports both decimal units (KB = 1000 bytes) used by storage manufacturers and binary units (KiB = 1024 bytes) used by operating systems. Understanding both systems is essential when comparing storage capacities and file sizes across different platforms.
How to Use
Enter any value in the input field and select its current unit. The converter instantly displays the equivalent value in all other units simultaneously. Whether you are converting kilobytes to megabytes for a download estimate, gigabytes to terabytes for storage planning, or bytes to kibibytes for precise technical calculations, the results update in real time as you type.
Features
- Real-time conversion across all units as you type
- 10 simultaneous output units for at-a-glance comparison
- Both decimal (KB, MB, GB, TB, PB) and binary (KiB, MiB, GiB, TiB, PiB) units
- Large number formatting with exponential notation for very small values
- One-click copy for any converted value
Why Two Systems?
Hard drive and SSD manufacturers use decimal units where 1 kilobyte = 1000 bytes. This makes storage capacities appear larger on product packaging. However, operating systems like Windows, macOS, and Linux report file sizes using binary units where 1 kibibyte = 1024 bytes. This discrepancy explains why a 500 GB hard drive shows as approximately 465 GB in Windows. Our converter shows both systems so you can easily compare and understand the difference.
Privacy
All conversions happen locally in your browser. No data is transmitted.
Last reviewed: July 2026.