Convert between bytes, KB, MB, GB, TB, and PB instantly — with a toggle for binary (1024) or decimal (1000) base.
Binary uses 1024 as the base for each unit step (how operating systems typically calculate), while decimal uses 1000 (how storage manufacturers typically advertise capacity), leading to different reported sizes for the same data.
Manufacturers advertise storage using decimal (1000-based) units, while operating systems display capacity using binary (1024-based) units, making the same drive appear smaller in your OS than its advertised capacity.
Use decimal for how storage is typically marketed and sold, or binary to match what your operating system's file properties usually display.
This tool converts a file size value into all common units at once — bytes, kilobytes, megabytes, gigabytes, terabytes, and petabytes — with a toggle between binary (1024-based) and decimal (1000-based) calculation methods.
There are two competing conventions for calculating file size units, and the difference causes genuine confusion. The decimal convention treats 1 kilobyte as exactly 1,000 bytes, 1 megabyte as 1,000 kilobytes, and so on — this is how storage device manufacturers typically advertise capacity (a "1TB" drive means 1,000,000,000,000 bytes). The binary convention instead treats 1 kilobyte as 1,024 bytes (2¹⁰), 1 megabyte as 1,024 kilobytes, and so on — this is how most operating systems calculate and display file and storage sizes internally. Because 1024 is larger than 1000, the same physical amount of data reports as a smaller number in binary units than in decimal units.
This binary-vs-decimal mismatch is exactly why a drive advertised as "1TB" often shows something like "931 GB" in your operating system's file explorer — the manufacturer calculated 1TB using the decimal (1000-based) convention, while your OS displays the same physical capacity using the binary (1024-based) convention. No actual storage is lost; it's purely a difference in how the same number of bytes is being labeled.
To resolve this ambiguity, the International Electrotechnical Commission introduced distinct binary unit names — kibibyte (KiB), mebibyte (MiB), gibibyte (GiB) — specifically to mean the 1024-based units, leaving KB, MB, and GB to unambiguously mean the 1000-based decimal units. In practice, though, most software and marketing still use "KB," "MB," and "GB" loosely for both conventions, which is exactly why a converter with an explicit binary/decimal toggle is useful.
All conversions happen directly in your browser — no values are sent to a server.