The gibibyte, unit of digital data
The gibibyte is exactly 1 073 741 824 bytes, that is two to the thirtieth power, and 7.4 per cent more than a gigabyte. It is the unit a computer actually counts in when it addresses memory, and the one it usually refuses to name.
The name was invented to end a confusion. In 1998 the International Electrotechnical Commission published the binary prefixes kibi, mebi, gibi and their symbols Ki, Mi, Gi, built from the decimal prefixes and the word binary, so that gigabyte could go back to meaning a thousand million bytes and nothing else. Adoption split the industry: macOS moved to decimal units in 2009, so a disk shows the figure printed on its box, while Windows still divides by 2³⁰ and writes GB, which is why the same one-terabyte disk reads 931 GB there and 1 TB on a Mac.
The gibibyte in other units
| 1 GiB | 0.00107374 TB |
| 1 GiB | 1.07374 GB |
| 1 GiB | 1,074 MB |
| 1 GiB | 1,073,742 kB |
| 1 GiB | 1,073,741,824 B |
| 1 GiB | 0.000976563 TiB |
| 1 GiB | 1,024 MiB |
| 1 GiB | 8,590 Mb |
| 1 GiB | 8,589,934,592 bit |
| 1 GiB | 0.00000107374 PB |
| 1 GiB | 0.000000953674 PiB |
| 1 GiB | 1,048,576 KiB |
| 1 GiB | 8.58993 Gb |
Frequently asked questions
How many gigabytes are in a gibibyte?
1.073741824 exactly, so a gibibyte is 7.4 per cent larger than a gigabyte. The gap widens with each step: a tebibyte is 10 per cent larger than a terabyte, a pebibyte 12.6 per cent larger than a petabyte.
Why does my 1 TB disk show 931?
Because a terabyte is 10¹² bytes and the system divides that by 2⁴⁰, giving 931.32 gibibytes, then labels the result GB. The disk holds exactly what the box promised; the number on screen is in a different unit than the one it names.
Where does the name gibibyte come from?
From giga and binary, contracted by the IEC in 1998. Kibi, mebi, gibi, tebi and pebi are built the same way, and their symbols keep a capital and an i, Ki, Mi, Gi, Ti, Pi, which distinguishes them at a glance from k, M, G, T and P.