GB vs GiB (Binary vs Decimal)
Also known as: gb vs gib, why storage less than advertised
GB (gigabyte) and GiB (gibibyte) are two ways to count storage. A GB is defined as 1,000,000,000 bytes (decimal, 1000-based), while a GiB is 1,073,741,824 bytes (binary, 1024-based). Manufacturers label capacity in decimal GB, but phones often report it in binary, so a "128 GB" device shows less.
- 1 GB (decimal) = 1,000,000,000 bytes; 1 GiB (binary) = 1,073,741,824 bytes.
- A 128 GB drive shows about 119 GB because the OS divides by 1024-based units.
- The decimal-vs-binary gap is roughly 7% and grows with total capacity.
Why the two units exist
Computers address memory in powers of two, so a kilobyte was historically treated as 1024 bytes rather than 1000. To remove ambiguity, the IEC standardized binary prefixes in 1998: kibibyte (KiB) = 1024 bytes, mebibyte (MiB) = 1024 KiB, and gibibyte (GiB) = 1024 MiB = 1,073,741,824 bytes.
Under the SI (decimal) system, a gigabyte (GB) is exactly 1,000,000,000 bytes. Storage and flash manufacturers advertise capacity in these decimal GB, because that is the larger-sounding number for the same physical chips.
Why your phone shows less space
A drive sold as "128 GB" holds 128,000,000,000 bytes (decimal). When the operating system divides that by 1,073,741,824 to display binary gibibytes, it reports roughly 119 GB even though many UIs still print the label "GB". The bytes did not disappear; only the counting unit changed.
The gap grows with capacity: it is about 7% smaller than the box claims. On top of this, the operating system, system partition, and reserved space consume further capacity, which is why a brand-new phone never shows the full advertised figure as free. Cleanor measures real bytes recovered, so its savings estimates are unaffected by which unit your phone displays.