File Size Converter — MB, GB, TB, KB Online

What is the difference between KB and KiB?

1 KB (kilobyte) = 1,000 bytes in the SI (decimal) system used by storage manufacturers. 1 KiB (kibibyte) = 1,024 bytes in the IEC (binary) system used by operating systems and RAM specifications. The gap grows significantly at larger scales — a "500 GB" hard drive has only ~465 GiB of usable space as reported by Windows or macOS.

Why does my hard drive show less space than advertised?

Storage manufacturers use SI units (1 GB = 10⁹ bytes) because the numbers look larger in marketing. Operating systems report space in binary units (1 GiB = 2³⁰ bytes), which is a larger base. So a 1 TB drive (10¹² bytes) shows up as ~931 GiB in your OS — the bytes are identical, only the unit interpretation differs.

What are SI (decimal) units?

SI units follow powers of 1,000: 1 KB = 1,000 B, 1 MB = 1,000 KB, 1 GB = 1,000 MB, etc. These are used by hard drive manufacturers, network speed ratings, and the International System of Units (SI).

What are IEC (binary) units?

IEC units follow powers of 1,024: 1 KiB = 1,024 B, 1 MiB = 1,024 KiB, 1 GiB = 1,024 MiB, etc. These are used by operating systems (Windows, macOS, Linux) for RAM, file system sizes, and memory addresses.

How many bytes is 1 GB?

1 GB (gigabyte, SI) = 1,000,000,000 bytes (10⁹). 1 GiB (gibibyte, IEC) = 1,073,741,824 bytes (2³⁰). The two definitions diverge by about 7.4%.

What is the difference between Mbps and MB/s?

Mbps (megabits per second) and MB/s (megabytes per second) are both used for network speed, but they differ by a factor of 8. 1 byte = 8 bits, so 100 Mbps ÷ 8 = 12.5 MB/s. Internet providers advertise in Mbps; download managers show MB/s — so a "100 Mbps" plan delivers ~12.5 MB/s of actual file transfer speed.