Convert kilobyte to byte

The SI prefixes count in thousands: 1 kB = 1,000 bytes, 1 GB = 10⁹ bytes. Computers count in powers of two, and for those the IEC prefixes exist: 1 KiB = 1,024 bytes, 1 GiB = 2³⁰ = 1,073,741,824 bytes, about 7 % more. Disk and memory-card makers use the decimal units, most operating systems display the binary ones (Windows labels them 'GB' regardless), which is why a '1 TB' drive shows as 931 GB: 10¹² bytes is 931 GiB. Nothing is missing. RAM is the exception and is always sold in binary sizes: 16 GB of RAM really is 16 GiB.

A bit is a single 0 or 1, and a byte is eight of them, 256 possible values, enough for one Latin letter: a byte has been 8 bits since the IBM System/360 of 1964, and 'octet' says so explicitly, which is why French writes Mo rather than MB. Bits are counted where single ones matter – 16-bit audio, 24-bit colour, 256-bit keys, internet speeds – and bytes where data is stored: an emoji takes 4 bytes in UTF-8, a photo a few million, a film a few billion. Lower-case b is bits, capital B bytes.