Your target heart rate zone is the BPM range you want to stay in during your exercises to make sure you get the most out of your workouts. Your target heart rate during exercise is generally 60-80% of your max heart rate. An often-used formula to calculate your max heart rate is to subtract your age from 220. Example: If you’re 25 years old, take 220-25=195 (max heart rate). 60-80% of 195 is 117-156 bpm (target heart rate).