It's important to know your target heart rate, so you can ensure that you are exercising effectively and safely. Your target heart rate zone will help you determine if your intensity is where it should be to reach your goals. 

To figure out your target heart rate zone, you want to calculate your maximum heart rate. Subtract your age from 220 to find your maximum heart rate. You won't be exercising at your maximum heart rate - you will be exercising at a percentage of that. Beginners are going to want to stay in the 50-65% range of the maximum heart rate whereas more conditioned individuals will strive for a target heart rate zone of 65-85% (experienced exercisers will be in the 70-85% range).

For Example:  A 45-year-old intermediate exerciser would have the following calculation for Max Heart Rate:

220 – 45 years = 175 beats per minute, or bpm

To calculate her target heart rate zone (65-85%):
Max heart rate x target % = Target Heart Rate
175 x 65% (or .65) = 114 bpm
175 x 85% (or .85) = 149 bpm
This person’s target heart rate zone is 114 bpm to 149 bpm.

I like to take my pulse in 10-second segments, so I divide my target heart rate by 6 to figure out what it should be for a 10-second time frame. In the example above, the individual's target heart rate zone for a 10-second segment would be 19-25. I find that it's a lot easier to remember 19-25 versus 114-149.

Keep in mind that your heart rate can also be influenced by other factors including environmental conditions such as hot, humid temperatures, high altitudes as well as medications you are taking. If you are exercising above your range, you are going to want to back off a bit. If you aren't in your range, you will want to increase your intensity.

If your pulse is frequently too low or too high while you are exercising, you will want to consult your doctor - particularly if you also feeling pain, dizziness or shortness of breath.