Data Storage Converter

This converter turns an amount of data in bytes, kilobytes, megabytes, gigabytes or terabytes into every other unit, using either the decimal standard (powers of 1,000) or the binary standard (powers of 1,024). It also shows how Windows would report a decimal size, which answers the most common question about storage: why a new drive, phone or memory card shows less space than advertised.

No space is missing. Manufacturers, macOS, iOS and network speeds use decimal units; Windows and RAM sizes use binary units but label them with the decimal names KB, MB and GB. The formal binary names — KiB, MiB, GiB, TiB — exist to remove the ambiguity, but are rarely shown to consumers.

Formatting a drive also reserves some space for the file system, and phones and computers set aside room for the operating system, so usable space is a little lower again. To estimate how long a file takes to transfer, use the download time calculator.

The decimal prefixes are SI prefixes defined by the BIPM; the binary prefixes were standardized by the International Electrotechnical Commission in 1998 and are now part of IEC 80000-13. The "Shown by Windows" figure applies the binary divisor to the bytes, which is what Windows File Explorer does even though it labels the result GB. Data rates (Mbps, Gbps) always use decimal prefixes and bits, not bytes.

The difference is small for kilobytes but grows by about 2.4 percentage points with each step up, which is why it is most noticeable on large drives.

• Decimal (1,000): hard drive, SSD, USB stick and memory card capacities; macOS (since Mac OS X 10.6) and iOS storage displays; most Linux desktop file managers; internet and network speeds; cloud storage plans.
• Binary (1,024): Windows File Explorer, RAM and cache sizes, and many command-line tools.

Because Windows and macOS count differently, the same file can show as different sizes on each. A video that macOS reports as 4.3 GB appears as about 4.0 GB in Windows.

Storage is measured in bytes (B) and connection speeds in bits (b) per second. One byte is 8 bits, so a 100 Mbps connection moves at most 12.5 MB of data per second. Watch the capital B: 1 MB is a megabyte, 1 Mb a megabit. For estimating how much space recordings take, the video file size calculator converts bitrates into file sizes, and the base converter shows why powers of two such as 1,024 are round numbers in binary.