The missing gigabytes are not missing
Drive manufacturers define a gigabyte as 1,000,000,000 bytes. Operating systems define it as 1,073,741,824 — two to the thirtieth power. The same physical drive therefore reads as "1 TB" on the box and about 931 GB in your file manager.
The gap widens with size: it is roughly 2.4% at kilobytes but nearly 10% at terabytes. Nothing is lost; the two systems simply count differently.
Bits versus bytes
A byte is eight bits. Storage is measured in bytes, but network speeds are quoted in bits per second — which is why a "100 Mbps" connection downloads at about 12.5 MB/s at best.
The capital B means bytes, lowercase b means bits. It is a one-character difference with an eightfold consequence.
How much space things actually take
A high-quality photograph from a modern phone runs 3 to 5 MB. A minute of 1080p video is roughly 60 to 100 MB, and 4K four times that. A compressed music track is around 5 MB, an ebook under 1 MB, and a feature film between 1 and 8 GB depending on resolution and codec.
This is why video dominates storage planning while documents are effectively free. A thousand text files rarely fill what a single hour of 4K footage consumes.
Formatted capacity and overhead
Beyond the decimal-versus-binary difference, filesystems reserve space for their own structures — allocation tables, journals and metadata — typically a small percentage of the drive. Solid-state drives also reserve hidden capacity for wear levelling.
Filesystems also allocate in fixed blocks, so a 1 KB file may occupy 4 KB on disk. With thousands of very small files, that rounding becomes visible in the total.
Frequently asked questions
What are KiB, MiB and GiB? +
They are the unambiguous binary units — a GiB is exactly 1,073,741,824 bytes. They were standardised precisely to end this confusion, though consumer software largely ignores them.
Why does my 1 TB drive show 931 GB? +
The manufacturer counts 1 TB as 10¹² bytes; the operating system divides by 2⁴⁰. Same drive, two counting conventions, roughly 9% apparent difference.
What comes after a terabyte? +
Petabyte, exabyte, zettabyte and yottabyte, each a further factor of 1,024 in binary terms.