STEP (ISO/DIS 10303-41, S96 ff) stützt sich bzgl. SI-Einheiten auf die folgenden sieben Basis-Einheiten ab:
 
lenght (metre),
 
mass (gram),
 
time (second),
 
electric_current (ampere),
 
thermodynamic_temperature (kelvin),
 
amount_of_substance (mole; quantiy; compared to the number of atoms in 0.012 kilogram of carbon 12),
 
luminous_intensity (candela).