Kinetics of niobium and titanium carbide precipitates in iron has been simulated with cluster dynamics. The simulations, carried out in austenite and ferrite for niobium carbides, respectively in austenite for titanium carbide, were analyzed for dependency on temperature, solute concentration, and initial cluster distribution. The results are presented for different temperatures and solute concentrations and compared to available experimental data. They show little impact of initial cluster distribution beyond a certain relaxation time and that highly dilute alloys with only monomers present a significantly different behavior than less dilute alloys or alloys with different initial cluster distribution.