Yottameter - Greatest, 10^24
Zettameter (10^21)
Exameter (10^18)
Petameter (10^15)
Terameter (10^12) 10x dist. from earth to sun
Gigameter (10^9)
Megameter (10^6)
Kilometer (10^3)     normal driving measure
Hectometer (10^2)
Decameter (10^1) 
Meter (10^0)           base measurement
Decimeter (10^-1)
Centimeter (10^-2)
Millimeter (10^-3)    smallest on normal ruler
Micrometer (10^-6)
Nanometer (10^-9) atomic size
Picometer (10^-12)
Femtometer (10^-15)
Attometer (10^-18)              
Zeptometer (10^-21)
Yoctometer - Smallest (10^-24)