Understanding Digital Storage Sizes: Bits, Bytes, and Beyond

Everything digital reduces to bits — single 1s and 0s. Eight bits make a byte, enough to store one letter of text. From there, the SI prefixes take over: a kilobyte is 1,000 bytes, a megabyte 1,000 kilobytes, a gigabyte 1,000 megabytes, and a terabyte 1,000 gigabytes.

The 1,000 vs 1,024 problem

Computers natively count in powers of two, and 2¹⁰ = 1,024 is close to 1,000. Early engineers borrowed 'kilo' to mean 1,024 bytes, and the ambiguity stuck. In 1998 the IEC introduced binary names to end the confusion: a kibibyte (KiB) is exactly 1,024 bytes, a mebibyte (MiB) is 1,024 KiB, and so on.

• 1 KB (kilobyte) = 1,000 bytes — used by drive manufacturers
• 1 KiB (kibibyte) = 1,024 bytes — used by most operating systems
• 1 GB = 1,000 MB (decimal) vs 1 GiB = 1,024 MiB (binary)

Why your 1 TB drive shows 931 GB

Manufacturers sell capacity in decimal terabytes: 1 TB = 1,000,000,000,000 bytes. Windows reports in binary gibibytes, where 1 GiB = 1,073,741,824 bytes. Divide the manufacturer's bytes by the operating system's larger unit and you get about 931 GiB. Nothing is missing — it's just unit conversion.

Our data storage converter uses the decimal SI convention, matching drive manufacturers and network equipment, so 1 GB = 1,000 MB exactly.

Capacity is not download speed

A download advertised at 100 Mbps is measured in megabits per second, while a file may be measured in megabytes. Divide bits by eight to get bytes: 100 Mbps has a theoretical maximum of 12.5 MB per second before network overhead. A 1 GB decimal file would therefore take at least 80 seconds under ideal conditions; real networks commonly take longer.

When checking a device's free space, also account for formatting and system files. Those uses are separate from the decimal-versus-binary naming difference that makes advertised and displayed capacity appear unequal.