SI System v/s IEC System

In computing, binary prefixes can be used to quantify large numbers where powers of two are more useful than powers of ten. Each successive prefix is multiplied by 1024(2¹⁰) rather than the 1000 (10³) used by the SI prefix system. Despite the ambiguity, binary prefixes are often written and pronounced identically to the SI prefixes, rather than using the IEC system.

In 1999, the international electro technical commission (IEC) published amendment 2 to “IEC 60027-2; letter symbols to be used in electrical technology-part 2; telecommunications and electronics”. This standard, which was approved in 1998, introduced the prefixes kibi-, mebi-, gibi-, tebi-, pebi-, exbi-, to be used in specifying binary multiples of a quantity. The names come from the first two letters of the original SI prefixes followed by bi which is short for “binary”. It also clarifies that, from the point of view of the IEC, the SI prefixes only have their base-10 meaning and never have a base-2 meaning. So, here is how IEC proposes them to be used: