Metric Prefixes and SI Units

Contributors: JordanDee
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The beautiful thing about these metric prefixes is that, once you get the hang of conversion between a few of them, translating that ability to all the other prefixes is easy.

As a first simple example, lets translate 1 Ampere (A) into smaller values. A milliampere is 1 thousandth of the unit Ampere hence 1 Ampere is equal to 1000 milliamperes. Going further, 1 milliampere is equivalent to 1000 microamperes and so on. Going in the opposite direction, 1 Ampere is .001 Kiloampere, or 1000 Amperes is 1 Kiloampere. Now that's a lot of current!

As you may have noticed, switching between prefixes is the same as moving the decimal point over by 3 places. This is also the same as multiplying or dividing by 1000. When you're going up to a larger prefix, from Kilo to Mega for example, the decimal place is moved three places to the left. 100,000 Kilowatts equals 100 Megawatts. 10 Kilowatts equals .01 Megawatts. Mega is the prefix right above Kilo so regardless of whether we are talking about Watts, Amperes, Farads, or whatever unit, the movement of the decimal place by three positions to the left still works when moving up a prefix.

When moving down a prefix, let's say from nano- to pico-, the decimal place is moved three places to the right. 1 nanoFarad equals 1000 picoFarads. .5 nanoFarad equals 500 picoFarads. Here's a short list so you can see the pattern:

1 Giga- = 1000 Mega-
1 Mega- = 1000 Kilo-
1 Kilo- = 1000 units
1 unit = 1000 milli-
1 milli- = 1000 micro-

See the trend? Each prefix is a thousand times larger than the previous. While a little overwhelming at first, translation from one prefix to another eventually becomes second nature.