Prefixes

What is an engineering prefix?
It is also known as SI or metric prefix. It is the name or symbol that comes before a base unit of measurement. Each prefix has a specific value and affects the basic unit by that value. Only one prefix can be used at a time.

How to calculate the value of a prefix measurement?

1. First, determine the prefix and its value.
2. Multiply the measurement by the prefix value and that will be the final value.


• Using 5 kilometers as an example, the prefix is kilo. Using the table below, the value of kilo- is 1000. Thus, 5 kilometers is 5 * 1000 and that equals 5000 meters.


• Another example, consider 89 milligrams. The prefix is milli and milli has a value of .001. 89 milligrams is 89 * .001 which equals 0.089 grams.
  

How to convert from one prefix to another?

1. First, determine the prefix of the original and its value.
2. Then, determine the value of the prefix that you want to convert to.
3. The next step is to take the value of the original prefix and divide by the value of the new prefix.


4. Multiply your original value (don't include the prefix) by the value in step 3. The answer is the new value.


• Ex. Convert 50 kilograms to milligrams. First, the original prefix is kilo and its value is 1000. Second, the value of milli is .001. 1000 divided by .001 equals 1,000,000. The final step is to multiply 50 by 1,000,000 and the result is 50,000,000 mg. So 50 kilograms equal 50,000,000 milligrams.


• Quick shortcut: Once you are familiar with the prefixes, you should recognize them by their powers of tens. Then, conversion from one prefix to another will just involve shifting the decimal point left or right. Shift right when you are going from a higher prefix to a low and shift left when you are going from a lower to a higher one. The amount of times you shift depends on the difference in the powers of tens.
  

Here is a table with some of the most common prefixes used.

• Note that the symbols are case sensitive. The symbols M and m are not the same value.