Gigaoctet (Go)

The gigaoctet is a unit of digital information equal to one thousand million octets, or eight gigabits. Its symbol is Go. It is the unit in which most things people actually buy are sized: the memory in a computer, the storage in a phone, the monthly allowance on a mobile contract.

The reference points are familiar. A DVD holds 4.7 gigaoctets and a dual-layer disc 8.5. A Blu-ray holds 25 or 50. A feature film in high definition is 4 to 15 gigaoctets depending on compression, and in ultra-high definition 40 or more. A phone with 128 gigaoctets of storage holds roughly thirty thousand photographs, or a few hundred hours of music.

Memory sizes now sit in this range and are stated in gibioctets even when written as gigaoctets. A module labelled 8 GB holds 8 gibioctets, which is 8.59 gigaoctets, because memory addressing is binary and always has been. The same is true of processor caches and of the page tables that map memory, so anything on the memory side of a computer is binary while anything on the storage side is decimal.

That split is the source of the most familiar consumer complaint about units. A hard drive sold as one teraoctet holds a million million octets, which the operating system divides by 1,024 three times and reports as 931 gigaoctets. Nothing has been lost; the drive holds exactly what the box says, but the two are counting in different bases. Lawsuits over this were settled in the manufacturers' favour, since the decimal usage matches the metric system.

Mobile data allowances made the gigaoctet a household figure. A few gigaoctets a month was generous around 2012 and is now minimal, because video dominates: an hour of standard-definition streaming is about 0.7 gigaoctets, an hour in high definition around 3, and an hour in ultra-high definition 7 or more.

For scale in text, a gigaoctet holds around a thousand full-length books as plain text, or the complete works of most authors many times over. Digital storage stopped being a constraint on text decades ago, and every capacity discussion since has really been about images, sound and video.

One gigaoctet equals 1,000,000,000 octets, 1,000 megaoctets, 8 gigabits, or about 0.9313 gibioctets.

Gigaoctet conversion table