Decimal and Binary Prefixes – The SI system, a decimal system, measures units in powers of 10. The binary numeric system measure units in powers of 2. Numeric prefixes, such as kilo, mega, and tera, represent thousandfold increases from the preceding number or base number. If the base number is 1 then a kilo is 1,000 times that and a mega is 1,000 times a kilo. A decimal kilo is 10 to the power 3 (103) or 1,000. But a binary kilo is 2 to the power 10 (210) or 1024. Since it has a different value from the decimal kilo the prefix is changed to kibi. The following table lists the various decimal and binary prefix terms and their values;
When dealing with the capacity of computer memory or storage the binary prefix is more accurate, although the less accurate decimal prefixes are in common use.
See also the SI Units entry.