Monomer 1 is consumed with reaction rate:
with  the concentration of all the active chains terminating in monomer 1, summed over chain lengths.  is defined similarly for monomer 2.
Likewise the rate of disappearance for monomer 2 is:
Division of both equations by  followed by division of the first equation by the second yields:
The ratio of active center concentrations can be found using the steady state approximation, meaning that the concentration of each type of active center remains constant.
The rate of formation of active centers of monomer 1 () is equal to the rate of their destruction  () so that
or
Substituting into the ratio of monomer consumption rates yields the Mayo–Lewis equation after rearrangement: