Formulas are derived which may be used to calculate the maximum range of a radar set. It is shown that the maximum range obtainable with a given radar set depends upon (1) the energy in the pulse, i.e., the peak power times the time duration of the pulse or the average power divided by the pulse-recurrence frequency; (2) the transmitting and receiving antenna gains; (3) the transmission line, antenna, and transmit-receive-box losses; (4) the "effective width" or time duration of the transmitted pulses; (5) the "effective bandwidth" of the receiver; (6) the radio frequency of the transmitted waves; (7) the recurrence frequency of the transmitted pulses; (8) the "noise figure" of the receiver; (9) the cosmic, atmospheric, and man-made noise picked up by the antenna; (10) the attenuation during passage of the radio waves through the atmosphere due to the absorption by the atmospheric gases and rain drops; (11) the "effective echoing area" of the target; (12) the directivity of the transmitting and receiving antennas in elevation and azimuth, and (13) the effect of the ground, which, in turn, is inextricably associated with the particular site used, the height of the target above the ground, and the polarization of the transmitted radiowaves.