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What Are the Prefixes for SI Units?

In math, you often use prefixes to write large and small numbers in a simpler way. For example, 2 million byte is much easier to write as 2 megabyte or 2 MB, where M means “mega” and mega = 106 = 1000000.



giga G billion 109

mega M million 106

kilo k thousand 103

hecto h hundred 102

deka da ten 10

deci d one tenth 101

centi c one hundredth 102

milli m one thousandth 103

micro μ one millionth 106

nano n one billionth 109

Example 1

Uncle Sam bought 2.3 hectograms (hg) of candy when he was at the store. How many grams does that correspond to?

Hecto (h) means “hundred”. That means Uncle Sam bought

2.3hg = (2.3 100)g = 230g

of candy.

Example 2

One stage of the cycling race Tour de France can be 192 kilometers (km) long. How many meters is that?

Kilo (k) means “1000”. Thus, the boys ride

192km = (192 1000)m = 192000m.

The stage is 192000 meters.

Example 3

Albert Einstein was in the laboratory playing with a microscope. While playing, he saw an organism weighing 521 micrograms. How many grams is that?

Micro (μ) means millionth. Thus, the organism weighed

521μg = 521 1 1000000g = 0.000521g

521μg = 521 1 1000000g = 0.000521g

Note! You switch the prefix with the numeric value of the prefix.

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