File Size Converter

Convert between bytes, KB, MB, GB, TB in both decimal (SI) and binary (IEC) units.

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How it works

Enter a number and pick its unit. The tool converts to all other units simultaneously using two standards: SI (decimal, where 1 KB = 1,000 bytes, used by hard-drive manufacturers and network tools) and IEC (binary, where 1 KiB = 1,024 bytes, used by operating systems for RAM and file sizes). Results update instantly in your browser with no network request.

Common use cases

  • Converting download or upload sizes shown in different units.
  • Understanding why Windows shows a smaller file size than the label on a hard drive.
  • Checking whether a file fits within an email or upload size limit.

Frequently asked questions

What is the difference between KB and KiB?

KB (kilobyte) in SI = 1,000 bytes. KiB (kibibyte) in IEC = 1,024 bytes. Hard drives use SI; operating systems traditionally use binary, which is why a "500 GB" drive shows as ~465 GiB in Windows.

Does this support petabytes?

The tool covers bytes through terabytes, which covers the vast majority of everyday file sizes. Petabytes are outside typical consumer use.