The SI allows the sizes of units to be made bigger or smaller by the use of appropriate prefixes. For example, the electrical unit of a watt is not a big unit even in terms of ordinary household use, so it is generally used in terms of 1000 watts at a time. The prefix for 1000 is kilo so we use kilowatts[kW] as our unit of measurement. For makers of electricity, or bigger users such as industry, it is common to use megawatts[MW] or even gigawatts[GW]. The most common are:

To be technically correct, all of the S I prefixes are multiples or sub-multiples of 1000. However, these are inconvenient for many purposes and so hecta (x 100), deca (x 10), deci (x 0.1), and centi (x 0.01) are commonly used.

The full range of prefixes with their [symbols or abbreviations] and their multiplying factors are;

[*] the symbol used here is the Greek letter known as 'mu'

Return to the top of this document