Flex Your Math Skills: Calculating Target Heart Rate

Ever wonder how hard you’re really working while exercising? Stop wondering and start counting! Here is a handy formula to help determine if you’re hitting your Target Heart Rate during exercise. If the mere mention of the word “formula” sends you into math anxiety, be rest assured that this is a simple mathematical calculation that even I, the descendant of a long line of math-phobes, can master.

Begin by assessing your Maximum Heart Rate (MHR). You can find this by taking the number 220 and subtracting your age. So for a thirty-year-old exerciser, the equation would look like this:

220 – 30 = 190 (MHR)

Next, calculate your Target Heart Rate (THR) range by multiplying your MHR by 60 percent and 80 percent. To reap the full benefits of cardiovascular exercise, you should aim to exercise at an intensity level of 60 to 80 percent of your maximum heart rate for about 30 minutes, 5 days a week. Here’s the equation for that thirty-year-old exerciser:

190 (MHR) x .60 = 114
190 (MHR) x .80 = 152

At the height of their cardio segment, the heart rate should be between 114 and 152 beats per minute. How do you find your heart rate? More math!

Before your cool down session, find your pulse at either your wrist or neck. Use two fingers and press lightly. Remain standing. Watch the second hand on your watch or a clock and count the number of beats you feel for 10 seconds. It’s helpful to turn off any music so that you’re not distracted by the beat of the song. So let’s imagine our thirty-year-old exerciser gave it their all during a Spinning class, and clocked in with 22 beats during the pre-cool-down 10-second heart rate check. To calculate how many beats that is in a whole minute, multiply it by six:

22 x 6 = 132 beats per minute (BPM)

As you can see, the THR is within the desired range of 114 to 152 beats per minute. If the heart rate is below  target, then you know to pump up the intensity during the next workout. If it exceeds the target range, then adjust the workout accordingly to prevent injury.

All this sounds simple enough, but like most things in life, there’s a catch. Although this method of determining target heart rate has been the standard for years, it’s not perfect. For one thing, it doesn’t apply to children or people taking heart medication. Second, the calculation for maximum heart rate (220 – your age) is based on population averages, and doesn’t take into account other factors like fitness level, genetics, or gender.

But before you give up and spring for a fancy $150 heart rate monitor, keep in mind that except for the elite athlete, this formula does work well when done in conjunction with a handy system called Rating of Perceived Exertion (RPE). Exercisers can use the RPE chart to subjectively rate how hard they’re working. A rating of 6 is deemed very, very light. A 13 is somewhat hard, and a rating of 19 is very, very hard. There are a number of ratings between these parameters, and many samples of the chart on the web. Although it sounds rudimentary, studies have shown that the RPE scale is a relatively reliable method in determining exercise intensity. Most people accurately classify how hard they’re working during exercise. It turns out we’re pretty darn good at reading our own body!

Of course, we don’t want to leave all the mathematical fun for the grown-ups. Check back here for a few fun lessons kids can learn while exploring exercise and heart rate.