File Size Converter
Convert file sizes between bytes, kilobytes, megabytes, gigabytes, and terabytes, in decimal or binary units.
About File Size Converter
A file size converter settles a confusion that trips up almost everyone working with digital storage: whether a gigabyte is 1000 megabytes or 1024. Drive makers sell you decimal units, while operating systems often report binary ones, which is why the same file shows different numbers in Windows and macOS. This tool converts between bytes and larger units with either convention, so you always know what you're actually looking at.
In decimal units, each step up divides or multiplies by 1000, so 1 GB equals 1000 MB. In binary units, each step uses 1024, so 1 GiB equals 1024 MiB. The tool lets you switch between the two, showing results that match how your operating system or your storage vendor reports sizes. That makes the apparent discrepancy between advertised and actual capacity easy to explain and to compute.
IT professionals calculating storage requirements and transfer times, and anyone buying hard drives or cloud storage, use it to reconcile marketing sizes with real usable space. Developers sizing caches, logs, and upload limits in code, and students learning about binary versus decimal prefixes, will find the dual convention invaluable. Photo and video editors estimating how much footage fits on a card also reach for it regularly.
How to Use
- Enter a file size value.
- Choose the unit you have and the unit you want.
- Switch between decimal (1000) and binary (1024) units as needed.
Example
1.5 GB to MB (decimal) 1500 MB
In decimal units, 1 GB = 1000 MB, so 1.5 GB = 1500 MB. Windows uses binary units where 1 GB = 1024 MB.
FAQ
Why do my files show a different size in Windows vs. macOS?
macOS reports decimal units (1000 bytes = 1 KB) while Windows uses binary units (1024 bytes = 1 KB), causing small differences.
What is the difference between KB and KiB?
KB is decimal (1000 bytes), KiB is binary (1024 bytes). This tool lets you choose which convention matches your context.
Which unit should I use?
Use decimal for storage advertised by drive makers and web services; use binary when comparing with OS-reported file sizes.
Why does a 1 TB drive show only about 931 GB on my computer?
The drive is 1 terabyte in decimal terms (1,000,000,000,000 bytes), but the OS reports in binary, where that works out to roughly 931 GiB. The bytes are the same; the unit convention differs.
Which convention should I use for transfer speed estimates?
Use decimal, since network speeds and transfer rates are quoted in decimal units. That gives a more accurate time estimate than mixing binary file sizes with decimal speeds.