The Flory–Stockmayer Theory predicts the gel point for the system consisting of three types of monomer units
:linear units with two A-groups (concentration ), 
:linear units with two B groups  (concentration ),
:branched A units (concentration ).
The following definitions are used to formally define the system
The theory states that the gelation occurs only if , where
is the critical value for cross-linking and  is presented as a function of ,
or, alternatively, as a function of ,
One may now substitute expressions for  into definition of  and obtain 
the critical values of  that admit gelation. Thus gelation occurs if
alternatively, the same condition for  reads,
The both inequalities are equivalent and one may use the one that is more convenient. For instance, depending on which conversion  or  is resolved  analytically.