This formula is one of the most effective methods used to calculate your target heart rate for aerobic (cardio) exercise. To accurately measure your resting heart rate: Count your pulse on your wrist (radial pulse) or on the side of your neck (carotid pulse) - prior to getting out of bed in the morning. Count the number of beats, starting with zero, for one full minute. For accuracy, take your resting heart rate three mornings in a row and average the heart rates.