In order to find the best “zone” for your goals and activity, you must first know how to calculate your maximum heart rate. The following formula offers a rough baseline: 220 – Age = maximum heart rate (MHR).

For endurance training and general aerobic conditioning, calculate 50 to 65 percent of your maximum heart rate if you’re a beginner; 60 to 75 percent for intermediate level exercisers; and 70 to 85 percent for established aerobic exercisers.

My current average heart rate max is 194 beats per minute (bpm). To work in the moderate to hard zone the 70% to 85% of my heart rate max as a 26 year old female would be 137 - 164 bpm. - ACSM Guidelines.