Abstract: A process of using a heart rate monitor to construct a user's personal heart rate curve, and using the heart rate curve to forecast the user's personal caloric expenditure on the basis of the user's heart rate while walking or running. A sub-unit installed within or otherwise connected to the electronic circuitry of a conventional heart rate monitor operates under control of a microprocessor. The sub-unit receives exogenous inputs by the user for conducting various calculations from a plurality of test data which is stored in memory by the user. The sub-unit utilizes the test data to calculate a rate of calories burned per pound for each test exercise, where the calculation is performed using a pre-programmed formula which differs according to the form of exercise. Next the sub-unit calculates a rate of calories burned per minute for each test exercise by multiplying the user's weight by the previously calculate rate per pound.