A pulse interval to pulse rate converter for use in a portable, battery-powered, hand-held test instrument useful for evaluating the performance of a pulse generator such as a cardiac pacer or the like. A pulse generator being tested generates output pulses at an unknown rate and it is desired to measure this rate and to visually display same in units of pulses per minute. A count representative of the interval between successive pulses is developed in a first digital counter and subsequently stored in a holding register, thereby freeing the first counter to continue to measure subsequent pulse-to-pulse intervals. A digital downcounter, arranged to be decremented at a fixed high rate, receives the stored interval value and a tally is developed in a display counter of the number of times that the interval value can be decremented to zero within a known time period, e.g., one second. The count developed in the display counter thus corresponds to the rate value expressed in units of pulses per minute (ppm).