Convert between data size units instantly. Supports both decimal (SI) units like KB, MB, GB and binary (IEC) units like KiB, MiB, GiB. Click any value to copy it.
Last updated: March 2026
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Frequently Asked Questions
What is the difference between KB and KiB (binary vs decimal)?
KB (kilobyte) uses the SI decimal standard: 1 KB = 1,000 bytes. KiB (kibibyte) uses the IEC binary standard: 1 KiB = 1,024 bytes. The distinction matters because storage manufacturers use decimal (making drives appear larger), while operating systems traditionally use binary (showing less usable space). The IEC introduced binary prefixes (KiB, MiB, GiB) in 1998 to eliminate this confusion.
How many bytes are in a gigabyte?
In decimal (SI): 1 GB = 1,000,000,000 bytes (109). In binary (IEC): 1 GiB = 1,073,741,824 bytes (230). The difference is about 7.4%. For a 500 GB hard drive, that translates to roughly 35 GB of apparent "missing" space when your OS reports in GiB.
Why does my hard drive show less space than advertised?
Drive manufacturers measure in decimal gigabytes (1 GB = 1 billion bytes) because it yields larger numbers for marketing. Windows displays sizes in binary gibibytes (1 GiB = 1,073,741,824 bytes). So a 1 TB drive (1,000,000,000,000 bytes) shows as ~931 GiB in Windows. macOS switched to decimal display in 2009, so Macs show the advertised capacity.