Step 1. Calculate maximum heart rate (MHR): Subtract your age from 220
Step 2. Depending upon your fitness level and your fitness goals, calculate your THR by multiplying your MHR by 60% - 75%
Example for a person age 40,
220 - 40 = 160
160 x 60% = 96
160 x 75% = 120
So the target heart rate zone for a 40 year old, assuming average physical condition and absence of physical restrictions, would be between 96-120 BPM.
An easy way to take your pulse to determine your approximate BPM is to lightly place your index and middle fingers together at your carotid artery (just under your jaw bone), count your pulse for 6 seconds and multiply by 10.
For additional information on target heart rates and physical fitness levels please consult the American Heart Association, or the American College of Sports Medicine. Always consult your physician before beginning any exercise program.