ESDU AERO S.00.03.15 provides curves of the ratios of total pressure across the shock ahead of the tube and of the static pressure upstream of the shock to the total pressure downstream of the shock both plotted against upstream Mach number. It is explained that it is usually sufficiently accurate to assume that a normal shock exists ahead of the unyawed tube and that there are no loses between the shock and the tube; it is therefore possible to determine the upstream Mach number and static pressure from those curves for the recorded value of downstream total pressure. Also given is the isentropic ratio of upstream static pressure to total pressure from which the Mach number in subsonic flow may be determined since the unyawed pitot then records upstream total pressure. Comments on the design of pitot static tubes are included.