In order to calculate your Target Heart Rate one needs to first find their pulse. You can find your pulse in your neck (Carotid artery) or your radial pulse(thumb side of wrist). Secondly, once you have found your pulse you will need to count the beats for 6 seconds. Take that number and times the number by 10. This is your or heart rate itself for one minute. The formula for one to figure out their THR is 220 minus your age times your fitness level. How do you know what your fitness level is? If you are not in great shape use 70%, 80% for average shape and 90% for excellent shape. For example, 220-40=180x .80=144 beats per minute. The target heart rate for a 40 year old with an 80% fitness level would be 144 BPM. Try it for yourself!!!!