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Reference Tables -- SI / Metric Unit Prefixes

 

Metric Prefixes

To help the SI units apply to a wide range of phenomena, the 19th General Conference on Weights and Measures in 1991 extended the list of metric prefixes so that it reaches from yotta- at 1024 (one septillion) to yocto- at 10-24 (one septillionth). Here are the metric prefixes, with their numerical equivalents stated in the American system for naming large numbers:

 
SI Unit Prefixes

Prefix

Symbol Meaning Base Unit Multiplied by Factor
yotta- Y septillion
1,000,000,000,000,000,000,000,000
1024
zetta- Z sextillion
1,000,000,000,000,000,000,000
1021
exa- E quintillion
1,000,000,000,000,000,000
1018
peta-
p quadrillion
1,000,000,000,000,000
1015
tera- T trillion
1,000,000,000,000
1012
giga- g billion
1,000,000,000
109
mega- M million
1,000,000
106
kilo- k thousand
1,000
103
hecto- h hundred
100
102
deca- da ten
10
101
Base units, no prefix - Ex.- meter, liter, gram 100
deci- d tenth
0.1
10-1
centi- c hundredth
0.01
10-2
milli- m thousandth
0.001
10-3
micro- u millionth
0.000001
10-6
nano- n billionth
0.000000001
10-9
pico- p trillionth
0.000000000001
10-12
femto-
f quadrillionth
0.000000000000001
10-15
atto- a quintillionth
0.000000000000000001
10-18
zepto- z sextillionth
0.000000000000000000001
10-21
yocto- y septillionth
0.000000000000000000000001
10-24


What's it all mean?
A kilometer is a thousand meters, a kiloliter is a thousand liters, a kilogram is a thousand grams; a centimeter is a hundredth of a meter, a centiliter is a hundredth of a liter, a centigram is a hundredth of a gram. The prefixes can be applied to any kind of SI unit. Only temperature degrees (Celsius or Kelvin in SI) seem to be exempt. Also, there is no accepted metric time system in use.



 

 


 

 

 

 

 


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