Relations are presented which permit a rapid calculation of friction and heat transfer from two-dimensional high-velocity flow to surfaces with locally constant pressure and temperature and with laminar and turbulent boundary layers. The calculation procedure is one which has been well established in the field of heat transfer, namely, to use equations for friction and heat-transfer parameters which have been developed for constant-property fluids and to adapt them to conditions where properties vary in such a way that those properties are introduced into the equations at a properly determined reference temperature. Relations are developed for this reference temperature which make the results of the outlined method agree best with published laminar boundary-layer solutions. The same relations turn out to give also good representation of measured results on turbulent boundary layers. The following advantages are connected with this particular method. It gives answers by simple calculations and it is quite generally applicable. The friction and heat-transfer equations are valid for any fluid gas or liquid. The relation for the reference temperature (or enthalpy), gives very good agreement with boundary-layer solutions regardless of the specific variation of the property values on which the calculations had been based. Therefore it may be expected that they are not only valid for air at any pressure and temperature level (as long as slip flow and dissociation are avoided) but approximate real conditions well also for other gases.