Find your target heart rate
The target heart rate (THR) is based on a percentage range of the maximum heart rate (MHR) for a particular age. THRs are also based on averages. Generally speaking, your maximum heart rate is figured at 220 minus your age. Thus, at 35 years of age, your MHR is 185 beats per minute (BPM)—t hat is, 220 minus 35.
The general rule of thumb is that for good health and wellness you need to be working your heart during activities between 50% and 75% of your MHR. The consensus from many health professionals is that the ideal is to spend at least 20 minutes in your "zone" (THR) three or more times a week.
Early on in your fitness program, you should stay at the lower end—50-60%, for 20-30 minutes. Later, you can gradually work up to the higher end of the range and longer time periods if you desire.
Those who are already fit and active may be able to exercise comfortably at up to 85% of their MHR, according to the American Heart Association. This is great for endurance (and endorphins!). However, you don't have to be at that level at all to get, or stay, in good physical shape. Do not start any exercise program without first consulting with and getting an OK from your doctor.
Age Target Heart Rate (THR): 50-75% 75-85% (Endurance)
20 100-150 Beats Per Minute (BPH) 150-170 BPM
30 95-142 BPM 143-162 BPM
40 90-135 BPM 135-153 BPM
45 88-131 BPM 131-148 BPM
50 85-127 BPM 127-144 BPM
55 83-123 PBM 123-140 BPM
60 80-120 BPM 120-136 BPM
65 78-116 BPM 116-131 BPM
70 75-113 BPM 112-127 BPM