SI prefixes

Symbol Prefix Factor Meaning
Y Yotta 1024 1,000,000,000,000,000,000,000,000
Z Zetta 1021 1,000,000,000,000,000,000,000
E Exa 1018 1,000,000,000,000,000,000
P Peta 1015 1,000,000,000,000,000
T Tera 1012 1,000,000,000,000
G Giga 109 1,000,000,000
M Mega 106 1,000,000
k Kilo 103 1,000
h Hecto 102 100
da Deca 101 10
UNITY -------- 100 1
d deci 10-1 1 / 10
c centi 10-2 1 / 100
m Milli 10-3 1 / 1,000
μ Micro 10-6 1 / 1,000,000
n Nano 10-9 1 / 1,000,000,000
p Pico 10-12 1 / 1,000,000,000,000
f Femto 10-15 1 / 1,000,000,000,000,000
a Atto 10-18 1 / 1,000,000,000,000,000,000
z Zepto 10-21 1 / 1,000,000,000,000,000,000,000
y Yokto 10-24 1 / 1,000,000,000,000,000,000,000,000

When dealing with computers things are a bit different see below

Symbol Prefix Factor Meaning
P Peta 250 1125899906842624
T Tera 240 1099511627776
G Giga 230 1073741824
M Mega 220 1048576
k kilo 210 1024