Calculate your heart rate for a safe and effective workout. Monitoring your heart rate can help you get the most out of your workout. If you work too hard, you may injure yourself or burn out. If you're not working hard enough, you may not see the results you are hoping for. Unless you're exercising at the right pace, you may not be getting the full health benefits a cardiovascular workout can offer such as more stamina and stronger bones. How do you know if you're exercising at your optimal level? It's simple - just input your age, resting heart rate and exercise intensity level below to find your target heart rate.