Conversion Calculator

Data sizes carry a built-in ambiguity that trips up nearly everyone: the same prefix means two different numbers depending on who's counting. Storage vendors, ISPs, and the official SI standard use decimal — a kilobyte is 1,000 bytes, a megabyte 1,000,000, a gigabyte a billion. It's clean powers of ten. This converter shows the decimal units (KB, MB, GB, TB, PB) and the binary ones side by side precisely so the gap is visible.

Operating systems and memory, by contrast, count in binary, because computer addressing is built on powers of two. There a "kibibyte" (KiB) is 1,024 bytes — 2 to the tenth — a mebibyte is 1,024², a gibibyte 1,024³. The IEC introduced the -bi- prefixes (KiB, MiB, GiB) in 1998 to end the confusion, and this converter uses them for the binary column. They're the technically correct names for what Windows still misleadingly labels "GB."

The discrepancy is small at the bottom and grows alarmingly toward the top. A kilobyte and a kibibyte differ by only 2.4% (1000 vs 1024). But each step up multiplies the gap: by the gigabyte level it's about 7.4%, and by the terabyte level a decimal TB is only about 0.909 of a binary TiB — a 9% shortfall. That compounding is exactly why a drive's advertised capacity always looks bigger than what your computer reports.

This is the source of the eternal complaint that a new drive is "missing" space. A manufacturer sells a "1 TB" drive meaning 1,000,000,000,000 bytes — decimal. Your operating system then divides by 1,024³ to display gibibytes and reports roughly 931 GiB, or equivalently about 0.909 TiB. No bytes are missing; the drive is exactly as advertised. The vendor counted in decimal and the OS counted in binary, and the 9% gap is the difference between the two systems, nothing more.