Hecto (symbol: h) is a decimal unit prefix in the metric system denoting a factor of one hundred. It was adopted as a multiplier in 1795, and comes from the Greek ἑκατόν hekatón, meaning "hundred". In 19th century English it was sometimes spelled "hecato", in line with a puristic opinion by Thomas Young.^{[1]}^{[2]} Its unit symbol as an SI prefix in the International System of Units (SI) is the lower case letter h.
The prefix is rarely used in general, but has certain specific applications:
Prefix  Base 10  Decimal  Adoption ^{[nb 1]}  

Name  Symbol  
quetta  Q  10^{30}  1000000000000000000000000000000  2022^{[3]} 
ronna  R  10^{27}  1000000000000000000000000000  
yotta  Y  10^{24}  1000000000000000000000000  1991 
zetta  Z  10^{21}  1000000000000000000000  
exa  E  10^{18}  1000000000000000000  1975^{[4]} 
peta  P  10^{15}  1000000000000000  
tera  T  10^{12}  1000000000000  1960 
giga  G  10^{9}  1000000000  
mega  M  10^{6}  1000000  1873 
kilo  k  10^{3}  1000  1795 
hecto  h  10^{2}  100  
deca  da  10^{1}  10  
—  —  10^{0}  1  — 
deci  d  10^{−1}  0.1  1795 
centi  c  10^{−2}  0.01  
milli  m  10^{−3}  0.001  
micro  μ  10^{−6}  0.000001  1873 
nano  n  10^{−9}  0.000000001  1960 
pico  p  10^{−12}  0.000000000001  
femto  f  10^{−15}  0.000000000000001  1964 
atto  a  10^{−18}  0.000000000000000001  
zepto  z  10^{−21}  0.000000000000000000001  1991 
yocto  y  10^{−24}  0.000000000000000000000001  
ronto  r  10^{−27}  0.000000000000000000000000001  2022^{[3]} 
quecto  q  10^{−30}  0.000000000000000000000000000001  
