ESDU AERO S.00.03.22 gives equations for the enthalpy and the static pressure in the equilibrium zone behind the shock, and the density ratio across the shock, as functions of the upstream Mach number. The enthalpy is also a function of the upstream temperature, and the static pressure is also a function of the dimensionless enthalpy which itself is a function of the static pressure, and so obtaining a value for static pressure involves an iterative procedure, although only one step should be necessary. Values of enthalpy and static pressure are calculated from the equations, in the latter case using a guessed value for dimensionless enthalpy. Values of downstream temperature and dimensionless enthalpy are then taken from the curves in ESDU AERO 00.01.06 and a new value of static pressure may then be obtained using the new value of dimensionless enthalpy. The density ratio and the real gas factor are obtained from the equations and, taking the speed of sound from the curves of ESDU AERO 00.01.06, the downstream Mach number is calculated.