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 1024 (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

10^{24}

zetta 
Z 
sextillion 
1,000,000,000,000,000,000,000

10^{21} 
exa 
E 
quintillion 
1,000,000,000,000,000,000

10^{18}

peta

p 
quadrillion 
1,000,000,000,000,000

10^{15}

tera 
T 
trillion 
1,000,000,000,000

10^{12}

giga 
g 
billion 
1,000,000,000

10^{9} 
mega 
M 
million 
1,000,000

10^{6} 
kilo 
k 
thousand 
1,000

10^{3} 
hecto 
h 
hundred 
100

10^{2} 
deca 
da 
ten 
10

10^{1} 
Base
units, no prefix  Ex. meter,
liter, gram 
10^{0}

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.
