Purpose – To develop and find the effect of combination of four cycle design variables that minimizes the specific fuel consumption (sfc) of a turbofan engine.Design/methodology/approach – After choosing the four variables, namely bypass ratio (B), fan pressure ratio, overall pressure ratio, and turbine inlet temperature (T04), first the sfc was minimized without a minimum thrust constraint. Then, a minimum specific thrust constraint was introduced.Findings – The unconstrained‐specific thrust is a two‐dimensional optimization problem, whereas the specific thrust constrained problem was found to be a three‐dimensional one.Research limitations/implications – The variables B and i are limiting factors to further improvement, as set by their maximum practical values, whereas the other two variables are to be optimized.Practical implications – A very useful work, in which numerical optimization program was developed, for a turbofan cycle and could be extended to other cycles.Originality/value – This paper offe...